Front cover: Sacramento River near Colusa, California, with the Sutter Buttes in the background. 

(Photograph by Cathy Munday, U.S. Geological Survey)
Occurrence and Transport of Diazinon in the 

Sacramento River and Selected Tributaries, 

California, during Two Winter Storms, 

January–February 2001

By Peter D. Dileanis, David L. Brown, Donna L. Knifong, and Dina Saleh 

Sacramento, California

2003

Water-Resources Investigations Report 03-4111

U.S. GEOLOGICAL SURVEY

Prepared in cooperation with the

CALIFORNIA DEPARTMENT OF PESTICIDE REGULATION
U.S. DEPARTMENT OF THE INTERIOR

GALE A. NORTON, Secretary

U.S. GEOLOGICAL SURVEY

Charles G. Groat, Director

Any use of trade, product, or firm names in this publication is for descriptive purposes only and does 

not imply endorsement by the U.S. Government.

For additional information write to:

U.S. Geological Survey

Water Resources

Placer Hall, Suite 2012

6000 J Street

Sacramento, California 95819-6129

http://ca.water.usgs.gov

Copies of this report can be purchased from:

U.S. Geological Survey

Information Services

Building 810

Box 25286, Federal Center

Denver, CO 80225-0286
 iii

CONTENTS

Abstract ....................................................................................................................................................................................................... 1

Introduction ................................................................................................................................................................................................ 1

Environmental Setting of the Sacramento River Watershed ................................................................................................. 2

Acknowledgments ......................................................................................................................................................................... 5

Study Design and Methodology ............................................................................................................................................................. 5

Selection of Sampling Sites .......................................................................................................................................................... 5

Monitoring Periods and Sampling Frequency ........................................................................................................................... 8

Sample-Collection Methods ......................................................................................................................................................... 8

Laboratory Analytical Methods ................................................................................................................................................... 9

Stage and Streamflow Measurement ......................................................................................................................................... 9

Load Calculation Methods ............................................................................................................................................................ 11

Quality Assurance and Quality Control ....................................................................................................................................... 11

Hydrologic Conditions During the Study Period ................................................................................................................................... 12

Occurrence and Transport of Diazinon ................................................................................................................................................. 14

Diazinon Use in the Sacramento Valley ..................................................................................................................................... 14

Concentrations of Diazinon Observed during Storms .............................................................................................................. 30

Measured and Estimated Diazinon Loads at Monitoring Sites .............................................................................................. 41

Relation of Diazinon Loads to Use ............................................................................................................................................... 43

Summary ..................................................................................................................................................................................................... 44

References Cited ....................................................................................................................................................................................... 44
 v

FIGURES

Figure 1. Map showing Sampling sites in the Sacramento River watershed, California......................................................... 3

Figure 2. Map showing Land use in the Sacramento Valley, California ..................................................................................... 4

Figure 3. Graph showing Monthly rainfall in the Sacramento Valley, California. ..................................................................... 13

Figure 4. Graph showing Daily rainfall and reported diazinon use in the Sacramento Valley, California, 

during the 2000–2001 dormant spray season ................................................................................................................. 13

Figure 5. Graph showing Diazinon use in the Sacramento Valley, California, during dormant spray seasons from 

1993 to 2001........................................................................................................................................................................... 14

Figure 6. Graph and map showing Diazinon use upstream of Sacramento River at Tower Bridge (site 21)

(A) Daily diazinon use from December 1, 2000, to March 31, 2001 .............................................................................. 15

(B) Areal distribution of applications................................................................................................................................ 16

Figure 7. Graph and map showing Diazinon use upstream of Sacramento River at Alamar (site 20)

(A) Daily diazinon use from December 1, 2000, to March 31, 2001 .............................................................................. 17

(B) Areal distribution of applications................................................................................................................................ 18

Figure 8. Graph and map showing Diazinon use upstream of Bear River near Berry Road (site 19)

(A) Daily diazinon use from December 1, 1999, to March 30, 2000 .............................................................................. 19

(B) Areal distribution of applications................................................................................................................................ 20

Figure 9. Graph and map showing Diazinon use upstream of Feather River below Star Bend (site 18)

(A) Daily diazinon use from December 1, 1999, to March 30, 2000 .............................................................................. 21

(B) Areal distribution of applications................................................................................................................................ 22

Figure 10. Graph and map showing Diazinon use upstream of Jack Slough near Doc Adams Road (site 16)....................... 23

Figure 11. Graph and map showing Diazinon use upstream of Main Drainage Canal at Gridley Road (site 10).................... 24

Figure 12. Graph and map showing Diazinon use upstream of Butte Creek at Gridley Road (site 9)

(A) Daily diazinon use from December 1, 1999, to March 30, 2000 .............................................................................. 25

(B) Areal distribution of applications................................................................................................................................ 26

Figure 13. Graph and map showing Diazinon use upstream of Sacramento River at Colusa (site 8)

(A) Daily diazinon use from December 1, 1999, to March 30, 2000 .............................................................................. 27

(B) Areal distribution of applications................................................................................................................................ 28

Figure 14. Graphs showing Diazinon concentrations and streamflow at sampling sites in the Sacramento Valley, 

California, from January 23, 2000, to February 17, 2001 

(A) Sacramento River at Tower Bridge (site 21)............................................................................................................. 30

(B) Sacramento River at Alamar (site 20) ........................................................................................................................ 31

(C) Bear River near Berry Road (site 19).......................................................................................................................... 32

(D) Feather River below Star Bend (site 18) .................................................................................................................... 33

(E) Jack Slough near Doc Adams Road (site 16) ............................................................................................................ 34

(F) Butte Slough at Lower Pass Road (site 11)................................................................................................................ 35

(G) Main Drainage Canal at Gridley Road (site 10)......................................................................................................... 36

(H) Sacramento River at Colusa (site 8) ........................................................................................................................... 37

Figure 15. Graphs showing Diazinon concentrations and stream stage at sampling sites in the Sacramento Valley, 

California, from January 23, 2000, to February 16, 2001

(A) Wadsworth Canal at South Butte Road (site 12)...................................................................................................... 38

(B) Butte Creek at Gridley Road (site 9) from January 23, 2000, to February 16, 2001.............................................. 39

Figure 16. Graph showing Boxplots of diazinon concentrations at many of the sampling sites in the 

Sacramento Valley, California ........................................................................................................................................... 40

Figure 17. Graph showing Diazinon load in relation to use in six subbasins in the Sacramento Valley ................................. 43
 v

Table 1. Sites used to monitor the occurrence and transport of diazinon during the 2000–2001 

dormant spray season, Sacramento River watershed, California............................................................................... 6

Table 2. Diazinon use in selected subbasins during four time periods in the 2000–2001 dormant spray season, 

Sacramento Valley, California ........................................................................................................................................... 29

Table 3. Diazinon loads estimated for sites in the Sacramento Valley, California, during two storm-monitoring 

periods in 2001...................................................................................................................................................................... 42

Appendix 1. Table 1. Diazinon and methidathion concentrations in blank samples analyzed by the 

California Department of Fish and Game's Water Pollution Control Laboratory ...................................................... 48

Appendix 1. Table 2. Pesticide recovery from spiked samples analyzed by the California Department of Fish and 

Game Water Pollution Control Laboratory ..................................................................................................................... 49

Appendix 1. Table 3. Diazinon and methidathion concentrations in replicate samples from sites in the 

Sacramento River Basin, California, analyzed by the California Department of Fish and Game's

Water Pollution Control Laboratory ................................................................................................................................. 50

Appendix 1. Table 4. Pesticide concentrations in blank and replicate samples from sites in the Sacramento River 

Basin, California, analyzed by the U.S. Geological Survey National Water Quality Laboratory ........................... 51

Appendix 1. Table 5. Pesticide recovery from spiked samples analyzed by the U.S. Geological Survey 

National Water Quality Laboratory .................................................................................................................................. 55

Appendix 2. Table 1. Diazinon and methidathion concentrations in environmental samples from the

Sacramento River Basin, California, analyzed by the California Dept. of Fish and Game Water 

Pollution Control Laboratory ............................................................................................................................................. 56

Appendix 2. Table 2. Pesticide concentrations in environmental samples from the Sacramento River Basin,

California, and surrogate recovery analyzed by the U.S. Geological Survey National Water 

Quality Laboratory .............................................................................................................................................................. 63

Appendix 2. Table 3. Field measurements at sites in the Sacramento River Basin, California .................................................... 70
vi 

CONVERSION FACTORS, WATER QUALITY INFORMATION, 

ABBREVIATIONS, AND ACRONYMS

CONVERSION FACTORS 

Temperature in degrees Celsius (C) may be converted to degrees Fahrenheit (F) as follows:

F=1.8 C+32.

WATER QUALITY INFORMATION

Pesticide concentrations in water samples are given in nanograms per liter (ng/L). One thousand nanograms per liter is equivalent to 1 microgram per liter (μg/L) or 0.001 milligram per liter (mg/L). Nanograms per liter is equivalent to “parts per trillion” (ppt). Loads, distances, and area are given in 

English units.

ABBREVIATIONS AND ACRONYMS

μm micrometer

lb a.i. pounds active ingredient

ADCP acoustic Doppler current profiler

CDFG California Department of Fish and Game

CSUC California State University at Chico

lb/d pound per day

DPR California Department of Pesticide Regulations

DWR California Department of Water Resources

GC/MS gas chromatography with mass spectrometry

GC/ECD/TSD gas chromatography coupled with an electron capture detector and thermionic specific detector

GIS Geographic Information System

kHz kiloherz

L, liter

mL milliliter

ng/L nanogram per liter

NWQL National Water Quality Laboratory

PUR Pesticide Use Report

Regional Board Central Valley Regional Water Quality Control Board

SIM Selective ion monitoring

SOP Standard Operating Procedure

SRWP Sacramento River Watershed Program

TMDL Total Maximum Daily Load

UDSDA United States Department of Agriculture

USGS United States Geological Survey

Multiply By To obtain

foot (ft) 3.048 meter (m)

cubic foot per second (ft3/s) 0.02832 cubic meter per second (m3/s)

inch (in.) 2.54 centimeter (cm)

mile (mi) 1.6093 kilometer (km)

square mile mi2 12.590 square kilometer (km2)

pound (lb) 0.4546 kilogram (kg)
Occurrence and Transport of Diazinon in the Sacramento 

River and Selected Tributaries, California, during Two 

Winter Storms, January–February 2001

By Peter D. Dileanis1, David L. Brown2, Donna L. Knifong1, and Dina Saleh1

Abstract

Diazinon, an organophosphate insecticide, is applied as 

an orchard dormant spray in the Sacramento Valley during 

the winter months when the area receives most of its annual 

rainfall. During winter rainstorms that frequently follow 

dormant spray applications, some of the applied pesticide is 

transported in storm runoff to the Sacramento River and its 

tributaries. Diazinon is also used to control insect pests on 

residential and commercial properties in urban areas and is 

frequently detected in urban storm runoff draining into the 

Sacramento River system.

Between January 24 and February 14, 2001, diazinon 

concentrations and loads were measured in the Sacramento 

River and selected tributaries during two winter storms that 

occurred after dormant spray applications were made to 

orchards in the Sacramento Valley. Water samples were 

collected at 21 sites that represented agricultural and urban 

inputs on a variety of scales, from small tributaries and drains 

representing local land use to main-stem river sites 

representing regional effects. 

Concentrations of diazinon ranged from below 

laboratory reporting levels to 1,380 nanograms per liter 

(ng/L), with a median of 55 ng/L during the first monitored 

storm and 26 ng/L during the second. The highest 

concentrations were observed in small channels draining 

predominantly agricultural land.

About 26,000 pounds of diazinon were reported applied 

to agricultural land in the study area just before and during the 

monitoring period. About 0.2 percent of the applied 

insecticide appeared to be transported to the lower 

Sacramento River during that period. The source of about one 

third of the total load measured in the lower Sacramento 

River appears to be in the portion of the drainage basin 

upstream of the city of Colusa. About 12 percent of the 

diazinon load in the lower Sacramento River was transported 

from the Feather River Basin, which drains much of the 

mountainous eastern portions of the Sacramento River Basin. 

Diazinon use in the study area during the 2000–2001 

dormant spray season continued a declining trend observed 

since 1993. The maximum concentrations of diazinon 

observed during the last 2 years of monitoring were lower 

than concentrations observed in previous years when larger 

amounts of diazinon had been applied as dormant sprays.

Introduction

Diazinon is an organophosphate insecticide that is 

applied to nut and stone-fruit trees in the Sacramento Valley 

during their winter dormant period to control peach twig 

borer, San Jose scale, and mite pests. The dormant season 

occurs from December through March of most years, and is 

considered the best time to control these pests because the 

efficacy of pesticide applications is greatest before the trees 

develop a leaf canopy (Zalom and others, 1995). Diazinon is 

also used in home, garden, and commercial applications in 

urban and industrial areas of the watershed. 

1U.S. Geological Survey, Placer Hall, 6000 J Street, Sacramento, 

California 95819

2Bidwell Environmental Institute, California State University, Chico, 400 

West First Street, Chico, California 95929
2 Occurrence and Transport of Diazinon, Sacramento River and Selected Tributaries, Calif., during Two Winter Storms, 2001

The Sacramento Valley usually receives most of its 

annual rainfall during the period when dormant sprays are 

applied. Pesticide monitoring studies have shown that rain 

and associated surface runoff from winter storms facilitate 

the transport of diazinon from its point of application to the 

Sacramento River and its tributaries. Evidence for this mode 

of transport is supported by observations that diazinon has 

been detected more frequently in valley streams during the 

rainy season than at dry times of the year and the highest 

diazinon concentrations measured have been in winter storm 

runoff during the dormant-spray season (Foe and Sheipline, 

1993; MacCoy and others, 1995; Domagalski, 1996; 

Ganapathy and others, 1997; Nordmark, 1998, 1999; 

Nordmark and others, 1998; Holmes and others, 2000; 

Dileanis and others, 2002). Diazinon has also been detected 

in air samples and in rain collected during the dormant-spray 

season, indicating that atmospheric transport may play a role 

in the offsite movement of diazinon (Giddings and others, 

2000; Majewski and Baston, 2002). 

In the winter of 2000, the U.S. Geological Survey 

(USGS) began participating in a storm-runoff monitoring 

program in cooperation with the California Department of 

Pesticide Regulation (DPR) and with guidance from the 

Sacramento River Watershed Program (SRWP) and the 

Central Valley Regional Water Quality Control Board 

(Regional Board). The goal of the monitoring program was to 

characterize the occurrence and magnitude of diazinon 

contamination in Sacramento Valley streams and to 

determine the sources of the diazinon detected in the 

Sacramento and Feather Rivers. The monitoring program, 

designed to expand the knowledge base developed by 

previous monitoring studies, was initiated to support the 

development of a pesticide management plan and a Total 

Maximum Daily Load (TMDL) program for diazinon. 

Background information on the diazinon monitoring program 

and results from the winter 2000 storm monitoring are 

reported by Dileanis and others (2002).

This report presents the results of storm runoff 

monitoring during the winter of 2001. Between January 24 

and February 14, 2001, diazinon and other pesticide 

concentrations were monitored during two storms that 

occurred in the Sacramento Valley after dormant-spray 

applications had begun. Samples were collected at 21 sites 

throughout a period of 5 or more days that began when each 

storm began. Diazinon loads from selected subbasins were 

estimated for the monitoring periods in order to identify the 

largest sources of diazinon to the Sacramento and Feather 

Rivers. Data on pesticide use in these subbasins was 

incorporated into a Geographic Information System (GIS) 

coverage to estimate diazinon yields, the portion of applied 

diazinon that was transported to the rivers. 

Environmental Setting of the 

Sacramento River Watershed 

The Sacramento River watershed (fig. 1) drains more 

than 27,000 mi2 of land from its upper reaches near the 

California–Oregon border to its mouth 50 mi northeast of the 

city of San Francisco (Kahrl, 1979). The major land uses in 

the watershed are forestry, agriculture, urban, and mining. 

The Sacramento River and its numerous tributaries provide 

water for a multitude of beneficial uses including irrigation of 

agricultural lands, domestic water supply, aquatic habitat, 

and recreation. The Sacramento River’s largest natural 

tributary is the Feather River, which originates in the Sierra 

Nevada and drains much of the eastern area of the 

Sacramento River watershed. Many smaller tributaries 

originate in the coastal mountains and the Sierra Nevada. 

Wintertime streamflow in the watershed is affected by 

reservoir releases, storm runoff, and diversions to bypass 

channels used for flood control. Portions of Sacramento River 

streamflow are exported for agricultural and domestic use in 

the southern part of the state.

The middle and lower reaches of the Sacramento River 

flow through the Sacramento Valley, which forms the 

northern part of California’s prominent Central Valley. It is 

geographically continuous with the San Joaquin Valley to the 

south, but is defined by its distinct drainage basin. Beginning 

near the town of Red Bluff, the valley stretches about 150 mi 

to the southeast where it merges into the broad expanse of the 

Sacramento-San Joaquin River Delta, south of the 

Sacramento metropolitan area. The generally flat valley floor 

occupies about 5,000 mi2, its elevation decreasing almost 

imperceptibly from about 300 ft at its northern end to near sea 

level in the delta. 

Agriculture is the dominant land use on the valley floor, 

followed by urban development. Figure 2 shows the extent 

and distribution of agricultural and urban land use in the 

valley. The hot summer and temperate winter climate, 

combined with the availability of water for irrigation during 

the normally dry summer months, allows a wide variety of 

crops to be grown. Land once occupied by natural flood 

basins on either side of the Sacramento River is characterized 

by shallow ground water and silty, poorly draining soils. 

Much of this area is planted with rice. Row crops and 

orchards requiring well-drained land are grown on soil 

derived from alluvial fans or the coarser soils associated with 

stream channels. About 2,300 mi2 in the watershed are 

devoted to agricultural use. Stone-fruit and almond orchards 

occupy about 290 mi2, mostly in the northern and central 

parts of the valley (California Department. of Water 

Resources, 1990, 1994a, 1994b, 1995a, 1995b, 1995c, 1995d, 

2000).
Introduction 3

0 20 KILOMETERS

0 20 MILES

Yolo Bypass

38

30

39

30

122121

39

Natomas

Drain

Sacramento River at Hamilton City

Mud Creek at Chico

Lindo Channel at Chico

Big Chico Creek at Chico

Little Chico Creek

Big Chico Creek at River Road

Stony Creek at Highway 45

Sacramento River at Colusa

Butte Creek at Gridley Road

Main Drainage Canal at Gridley Road

Butte Slough at Lower Pass Road

Wadsworth Canal at South Butte Road

DWR Pump Plant 2, north

DWR Pump Plant 2, south

DWR Pump Plant 1

Jack Slough at Doc Adams Road

Feather River at Yuba City

Feather River below Star Bend

Bear River near Berry Road

Sacramento River at Alamar

Sacramento River at Tower Bridge

1

2

3

4

5

6

7

8

9

10

11

12

13

14

15

16

17

18

19

20

21

Canal

Main Drainage

Freemont

Weir

EXPLANATION

Site number and names

Sampling site

Stony C reek

Butte Creek

Big

Chico

Creek

Honcut Creek

Yuba River Jack Slough

Sacramento River

Feather River

Lake Oroville

Cherokee Ca nal

Colusa Basin Drain

Gilsizer Slough Sutter Bypass

Nato

masCross Canal

Bear River

Mud Creek

Little Chico Creek

Cana

B

l

utte Slough

Moulton

Weir

Colusa

Weir

Tisdale

Weir

Wadsworth

Sutter

Buttes

Yuba City

Marysville

Colusa

Nicolaus

Chico

Red Bluff

Sacramento

Freeport

Verona

1

7 6 4

5

3 2

17 12

11

20

18

15 19

13&14

21

16

8

9 10

Basin

boundary

Redding

Red Bluff

Chico

Colusa

Sacramento

Figure 1. Sampling sites in the Sacramento River watershed, California.
4 Occurrence and Transport of Diazinon, Sacramento River and Selected Tributaries, Calif., during Two Winter Storms, 2001

Almond

Prune

Peach/Nectarine

Other Agriculture

Urban

All other categories

Land Use

0 10 20 KILOMETERS

0 10 20 MILES

39

39

30

12230

40

122

Honcut Creek

Big

Chico

Creek

Feat her River

Stony C reek

Butte Creek

Bear River

Yuba River

Colusa Basin Drain

Red Bluff

Sacramento

River

Sutter

Buttes

Lake Oroville

Jack Slough

Main Drainage

Canal

Chico

Colusa

Yuba City

Marysville

Nicolaus

Sacramento

Verona

11

8

9 10

12 16

17

13&14

18

15 19

20

21

Sacramento River at Hamilton City

Mud Creek at Chico

Lindo Channel at Chico

Big Chico Creek at Chico

Little Chico Creek

Big Chico Creek at River Road

Stony Creek at Highway 45

Sacramento River at Colusa

Butte Creek at Gridley Road

Main Drainage Canal at Gridley Road

Butte Slough at Lower Pass Road

Wadsworth Canal at South Butte Road

DWR Pump Plant 2, north

DWR Pump Plant 2, south

DWR Pump Plant 1

Jack Slough at Doc Adams Road

Feather River at Yuba City

Feather River below Star Bend

Bear River near Berry Road

Sacramento River at Alamar

Sacramento River at Tower Bridge

1

2

3

4

5

6

7

8

9

10

11

12

13

14

15

16

17

18

19

20

21

EXPLANATION

Site number and names

Sampling site

1

7

2

3 4

5 6

Almond

Prune

Peach/Nectarine

Other Agriculture

Urban

All other categories

Land Use

0 10 20 KILOMETERS

0 10 20 MILES

39

39

30

12230

40

122

Honcut Creek

Big

Chico

Creek

Feat her River

Stony C reek

Butte Creek

Bear River

Yuba River

Colusa Basin Drain

Red Bluff

Sacramento

River

Sutter

Buttes

Lake Oroville

Jack Slough

Main Drainage

Canal

Chico

Colusa

Yuba City

Marysville

Nicolaus

Sacramento

Verona

11

8

9 10

12 16

17

13&14

18

15 19

20

21

Sacramento River at Hamilton City

Mud Creek at Chico

Lindo Channel at Chico

Big Chico Creek at Chico

Little Chico Creek

Big Chico Creek at River Road

Stony Creek at Highway 45

Sacramento River at Colusa

Butte Creek at Gridley Road

Main Drainage Canal at Gridley Road

Butte Slough at Lower Pass Road

Wadsworth Canal at South Butte Road

DWR Pump Plant 2, north

DWR Pump Plant 2, south

DWR Pump Plant 1

Jack Slough at Doc Adams Road

Feather River at Yuba City

Feather River below Star Bend

Bear River near Berry Road

Sacramento River at Alamar

Sacramento River at Tower Bridge

1

2

3

4

5

6

7

8

9

10

11

12

13

14

15

16

17

18

19

20

21

EXPLANATION

Site number and names

Sampling site

1

7

2

3 4

5 6

Figure 2. Land use in the Sacramento Valley, California. 

[Land use derived from California Department of Water Resources digital land-use data (California Department of Water Resources, 1990, 1994, 1995, 

2000).]
Study Design and Methodology 5

Most precipitation in the watershed occurs from 

November through March, with the largest amount, on 

average, during the month of January. With rare exceptions, 

precipitation on the valley floor falls as rain. Mean annual 

rainfall on the valley floor tends to increase with latitude and 

elevation, ranging from 22 in. at Sacramento to 30 in. at Red 

Bluff. In the higher elevations of the Sierra Nevada on the 

eastern boundary of the watershed, precipitation averages 80 

to 90 in. each year, primarily from heavy snowfall during the 

winter months (National Oceanic and Atmospheric 

Administration, 2001).

Acknowledgments

Kevin P. Bennett of the California Department of 

Pesticide Regulation led the study design team and was in 

charge of logistics for the 2001 monitoring year fieldwork. 

Field personnel included Kevin Kelley, Sainey Ceesay, Jesse 

Ybarra, Carissa Ganapathy, Amy Washburn, and Linda 

Rivard from the California Department of Pesticide 

Regulation; Mary Menconi, Sam Harder, Michele McGraw, 

Zhimin “Jamie” Lu, and Debbie Daniels from the Central 

Valley Regional Water Quality Control Board; Frank 

Moseanko, Jerry Harmon, and Jason May from the U.S. 

Geological Survey; and our colleagues from the California 

State University at Chico: Matt Bacior, Chris Bujalski, Vicky 

Snowden, Lisa Stultz, and Sara Taddo.

Study Design and Methodology 

Selection of Sampling Sites

Water samples were collected at 21 sites and analyzed 

for diazinon and other pesticides in order to monitor the 

occurrence and transport of the insecticide in storm runoff 

during the 2000–2001 dormant spray season. The locations of 

individual sampling sites are described in table 1 and shown 

on the map of the study area (fig. 1). Sites were chosen to 

represent the effects of upstream land use on a variety of 

scales, from small tributaries and drains representing local 

land use to main-stem river sites representing regional 

effects. Site selection criteria included historic or suspected 

diazinon use upstream, availability of streamflow data, 

accessibility during stormy weather, and the safety of field 

personnel.

Four sites (1, 8, 20, and 21) were located on the 

Sacramento River and two sites (17 and 18) on the Feather 

River to evaluate pesticide contamination in these large rivers 

that receive diazinon inputs from multiple upstream sources. 

Site 1, Sacramento River at Hamilton City (located near river 

mile 199), was farthest upstream and chosen to monitor the 

effect of pesticide sources in the northern portion of the 

watershed, which covers approximately 10,800 mi2 upstream 

of the site (U.S. Geological Survey, accessed February 3, 

2003). Winter streamflow at the site is largely a function of 

controlled water releases from Lake Shasta located 45 mi 

upstream and storm runoff from tributaries between the dam 

and Hamilton City. Land use near the Sacramento River 

upstream of site 1 is a mosaic of orchard, row crops, pockets 

of urban land use, and natural riparian forests in various 

stages of restoration. Air photos and previous field 

reconnaissance of the river indicate that many of the orchards 

directly adjoin the river with no apparent buffer strips or 

runoff control structures. 

Potential diazinon sources between site 1 and the next 

downstream monitoring location (site 8, Sacramento River at 

Colusa) at river mile 144 include Stony Creek, the Chico 

urban area, and orchards near the river. Nearly continuous 

leveed banks downstream of Stony Creek (river mile 172) 

restrict runoff inflow into the river, but there are numerous 

small pockets of orchard lands located within the leveed 

floodplain. 

Near flood stage, Sacramento River water is often 

diverted into leveed bypass channels that augment the limited 

capacity of the main river channel. At river mile 158, about 

13 mi upstream of Colusa, Moulton Weir can divert water to 

the east of the river channel, and at river mile 146, just 2 mi 

above site 8, water can be diverted east from the Colusa Weir. 

Water from both these weirs flows overland to Butte Slough 

and the Sutter Bypass channel, both of which flow southward. 

Water can also be diverted into the Sutter Bypass through 

Tisdale Weir at river mile 119. The Sutter Bypass merges 

back into the Sacramento River near the mouth of the Feather 

River. At this point (river mile 81) the Freemont Weir can 

divert a large portion of the Sacramento River flow southwest 

to the delta through the Yolo Bypass to prevent flooding in 

the Sacramento Metropolitan area.

Site 20, Sacramento River at Alamar (river mile 70), 

included additional sources from the Feather River, Butte 

Creek-Sutter Bypass, and Natomas Cross Canal subbasins. 

The site farthest downstream in the study area was site 21 

(Sacramento River at Tower Bridge), which combined 

diazinon from upstream sources with runoff from the 

northern part of the Sacramento metropolitan area.
6 Occurrence and Transport of Diazinon, Sacramento River and Selected Tributaries, Calif., during Two Winter Storms, 2001

Table 1. Sites used to monitor the occurrence and transport of diazinon during the 2000–2001 dormant spray season, Sacramento River watershed, California.

[DWR, California Department of Water Resources]

Site 

No. Site name Latitude Longitude Description

1 Sacramento River at Hamilton City 39°4507 1215938 Bridge on Highway 32 at Hamilton City

2 Mud Creek at Chico 39°4700 121°5313 Bridge at Esplanade Road northwest of Chico

3 Lindo Channel at Chico 39°4430 121°5248 Bridge on Highway 32 in Chico

4 Big Chico Creek at Chico 39°4338 121°5144 Bridge at Rose Avenue in Chico

5 Little Chico Creek 39°4312 121°5026 Bridge at Dayton Road in Chico

6 Big Chico Creek at River Road 39°4217 121°5617 Bridge on River Road (Sutter Avenue) southeast 

of Chico, just upstream of river mouth

7 Stony Creek at Highway 45 39°4238 122°0008 Bridge on Highway 45, 2 miles south of 

Hamilton City

8 Sacramento River at Colusa 39°1252 121°5957 Bridge on River Road in Colusa

9 Butte Creek at Gridley Road 39°2143 121°5330 Bridge on Gridley Road 10 miles west of 

Gridley

10 Main Drainage Canal at Gridley Road 39°2144 121°4923 Bridge on Gridley Road 6.5 miles west of 

Gridley

11 Butte Slough at Lower Pass Road 39°1116 121°5428 Bridge on Lower Pass Road, southeast of the 

Sutter Buttes

12 Wadsworth Canal at South Butte Road 39°0911 121°4400 Bridge on South Butte Road 15 miles west of 

Yuba City

13 DWR Pumping Plant 2, North (Obanion Outfall) 39°0133 121°4330 Pedestrian bridge just upstream of weir at 

pumping plant on west end of Obanion Ave

14 DWR Pumping Plant 2, South (Obanion Outfall) 39°0133 121°4330 Single-lane bridge just upstream of the pumping 

plant

15 DWR Pumping Plant 1 (Sacramento Outfall) 38°5560 121°3801 Samples collected from the bank of north drain 

at pumping plant near west end of 

Sacramento Ave

16 Jack Slough near Doc Adams Road 39°0943 121°3543 North bank of slough north of Marysville near 

Doc Adams Road

17 Feather River at Yuba City 39°0837 121°3626 West bank of river beneath Highway 20 bridge 

in Yuba City

18 Feather River below Star Bend 39°0020 121°3442 Samples collected from boat 8 miles upstream 

of Highway 99 bridge (near river mile 17)

19 Bear River near Berry Road 38°5718 121°3302 1 mile downstream of Highway 70 bridge. 

Waded at low flow; south bank at high flows 

20 Sacramento River at Alamar 38°4030 121°3736 Pier on east bank at river mile 71, just upstream 

of Highway 5 (Veteran's) bridge

21 Sacramento River at Tower Bridge 38°3430 121°3020 Tower Bridge on Capitol Avenue, downtown 

Sacramento
Study Design and Methodology 7

Streamflow at sites 17 and 18 on the Feather River is 

largely controlled by releases from Oroville Dam in the Sierra 

foothills. Prune, peach, and nectarine orchards occur 

throughout the lower watershed and dominate the landscape 

along the east and west sides of the Feather River (fig. 2). The 

channel is leveed throughout much of its lower reach below 

Lake Oroville, and most of the runoff from the orchards and 

urban areas west of the river levies flows southwest to the 

Butte Slough and Sutter Bypass before entering the 

Sacramento River just upstream of the mouth of the Feather 

River. Orchard runoff drains directly into the Feather River 

from orchards growing within the leveed channel and from 

east side tributaries. Site 17 (Feather River at Yuba City) is 

downstream of Honcut Creek and Jack Slough. Jack Slough 

was monitored just upstream of its confluence with the 

Feather River at site 16 because most of the orchards in its 

watershed are located close to the river. Site 18 (Feather 

River below Star Bend) was 11 mi downstream of site 17 and 

sampled by boat. The original sampling plan called for site 18 

to be located farther downstream below the mouth of the Bear 

River, but unusually low flow in the Feather River made 

access to the site difficult, so an alternate site was chosen 

where the channel is narrower and water depths were 

sufficient for the sampling boat. Access to site 17 was limited 

to the riverbank, and no streamflow data was available at this 

location. Site 18 was located on the Bear River, the largest 

tributary to the Feather River below Lake Oroville. 

Combined flows and loads of diazinon estimated at sites 18 

and 19 represent the total flow and load from the Feather 

River. 

 Diazinon transported in storm runoff from the city of 

Chico and the surrounding urban area was monitored at five 

sites on four creeks that flow through and drain the mostly 

commercial and residential urban lands. Data from the U.S. 

Census indicates that the rapidly growing population of 

Chico was 60,000 in 2000 and covered an area of 28 mi2

(U.S. Census Bureau, accessed April 18, 2003). The total 

population of the city and surrounding urban area was 

approximately 100,000. Flows in Mud Creek at Chico (site 

2), Big Chico Creek at Chico (site 4) and Big Chico Creek at 

River Road (site 6), and Little Chico Creek (site 5) combine 

discharge from urban runoff and from their watersheds in the 

Sierra foothills. The Lindo Channel at Chico (site 3) was 

created by enlarging a small distributary channel (Sandy 

Gulch) of Big Chico Creek to accommodate flows of 6,000 

ft3/s (U.S. Army Corps of Engineers, 1961). The urban area 

upstream of each sampling site was estimated using GIS data 

from the City of Chico Department of Public Works. Site 3 

on the Lindo Channel has the largest contributing area of 

approximately 5,200 acres. Site 2 on Mud Creek is next 

largest at 4,500 acres. The third largest at 4,200 acres is site 5 

on Little Chico Creek. The creation of parkland (Bidwell 

Park) and the California State University at Chico (CSUC) 

campus in the city’s early history constrained construction of 

storm sewer outfalls along Big Chico Creek. Because of these 

constraints the urban drainage area of Big Chico Creek at site 

4 just downstream of the city is only 890 acres. Big Chico 

Creek also was sampled 5.5 mi downstream of the Chico 

urban area and just upstream of its confluence with the 

Sacramento River (site 6). At this point, flows from Mud 

Creek and the Lindo Channel have entered the Big Chico 

Creek channel, creating a potential composite of runoff from 

approximately 72 percent of the Chico urban area. Little 

Chico Creek, draining the southeastern portions of the Chico 

urban area, flows south to eventually enter Butte Slough 

above site 11. 

Lower Stony Creek was monitored at site 7 about 3 mi 

upstream of its confluence with the Sacramento River. The 

Stony Creek watershed covers approximately 720 mi2

(Kondolf and Swanson, 1993) with elevations ranging from 

approximately 6,500 ft in the headwaters of the Coast Range 

to approximately 120 ft at its confluence with the Sacramento 

River. Black Butte Dam, located 21.5 mi upstream of site 7, 

exerts a major control on streamflow in the lower reach of 

Stony Creek. The dam is operated for flood control and 

irrigation water storage. Land use in the Stony Creek 

watershed is largely agricultural with grazing in the lower 

foothills trending to orchards and row crops close to the 

Sacramento River. The nearest stream gage to site 7 is located 

just below Black Butte Dam and is operated by the U.S. Army 

Corp of Engineers.
8 Occurrence and Transport of Diazinon, Sacramento River and Selected Tributaries, Calif., during Two Winter Storms, 2001

Butte Creek at Gridley Road (site 9) receives runoff 

from the Sierra foothills and mixed agricultural land that 

includes almond orchards southeast of Chico. The Main 

Drainage Canal at Gridley Road (site 10) conveys runoff 

from prune, peach, and nectarine orchards in the portion of 

the valley floor just west of the Feather River and north of the 

Sutter Buttes. Water from both these sites merges upstream of 

site 11 (Butte Slough at Lower Pass Road) before flowing 

into the Sutter Bypass. Runoff from orchards and urban areas 

east and southeast of the Sutter Buttes drains to the Sutter 

Bypass through the Wadsworth Canal at South Butte Road 

(site 12), or through channels leading to California 

Department of Water Resources (DWR) pumping plants 1 

and 2 (sites 13, 14, and 15). Two channels leading to DWR 

Pumping Plant 2 were monitored close to the pumps. Site 13 

drains the largely agricultural area to the north of the site, and 

site 14 drains both agricultural land and the Yuba City urban 

area. Site 15, at DWR Pumping Plant 1, appears to drain 

mostly agricultural land including orchards and rice fields.

Monitoring Periods and Sampling Frequency

Sample collection was scheduled to begin during the 

first large rainstorm to occur after a significant number of 

dormant spray applications had been made, and during a later 

storm that might occur after the number of applications had 

appeared to peak. Diazinon applications were monitored 

through field observations and conversations with the 

personnel at the California Department of Pesticide 

Regulation and agents in county agricultural commissioner 

offices. Storms with significant potential to produce runoff 

were those with at least 1/2 in. of rain if the preceding weeks 

had been dry, or about 1/3 in. of rain if the soil was saturated 

with water from recent rainfall.

Sample collection began on January 24, 2001, for the 

first monitored storm and on February 9 or 10 at sites 

monitored during the second storm. Sites 8, 11, and 13 

through 20 (see table 1) were sampled once each day for a 

period of five consecutive days after the beginning of each 

storm. Because site 21 (Sacramento River at Tower Bridge) 

is located many miles downstream of agricultural sources of 

diazinon, elevated concentrations at the site were expected to 

lag behind upstream sites and to remain elevated above prestorm levels for a longer period of time. Sampling at that site 

began on January 25 (a day later than the upstream sites) and 

a single sample collected each day until January 29, with an 

additional sample collected on January 31, 2 days after 

sampling ended at upstream sites. 

Samples were collected more frequently at sites 9, 10, 

and 12. These sites are located on smaller subbasins with 

extensive agricultural land use. Conditions were expected to 

change rapidly at these sites because of their proximity to 

diazinon sources and because the hydrologic characteristics 

of small subbasins are such that streamflow responds rapidly 

to storm runoff. Water samples at these sites were collected 

up to six times throughout each 24-hour period.

Samples were collected at site 1 (Sacramento River at 

Hamilton City), around the city of Chico (sites 2–6), and at 

site 7 (Stony Creek at Highway 45) during the second storm. 

Site 1 was sampled daily from February 9 to 14. Sites 2, 3, 

and 5 (Mud Creek at Chico, Lindo Channel at Chico, and 

Little Chico Creek) were sampled once each day on February 

9 and 10. The two sites on Big Chico Creek (sites 4 and 6) 

were sampled twice each day between February 9 and 12. At 

site 7, samples were collected once each day on February 9 

and 10.

Sample-Collection Methods

Samples at sites 1 through 7 were collected by personnel 

from CSUC, and samples from sites 18, 19, and 21 were 

collected by personnel from USGS. Samples at all other sites 

were collected by personnel from DPR and the Regional 

Board. 

At most sites water samples were collected from bridges 

using a US series D–77 sampler. Depth- integrated samples at 

a single point in the center of each channel were collected in 

a 3-L Teflon bottle mounted in the sampler. Teflon collection 

bottles were used to minimize contamination or loss of 

pesticide from sorption to container walls. Samples were 

usually collected at Bear River near Berry Road (site 19) by 

wading across the channel and collecting depth-integrated 

samples in a handheld sampler (DH–81 with 3-L Teflon 

bottle) at 5 to 10 equal-width increments. On February 12, 13, 

and 14, during the second storm monitoring period, 

streamflow was too high to wade the Bear River, so grab 

samples were collected in a 3-L Teflon bottle from the stream 

bank. Grab samples were collected at Lindo Channel at Chico 

(site 3) with a 3-L Teflon bottle because the water depths at 

the site were too shallow for a depth-integrating sampler. 

After vigorous mixing of the collected sample, subsamples 

were poured directly into baked amber 1-L glass bottles fitted 

with Teflon-lined caps. 
Study Design and Methodology 9

At Feather River below Star Bend (site 18), depthintegrated water samples were collected from a boat using a 

D–77 sampler at 7 to 10 points (equal-width increments) 

across the channel. The total volume of water collected along 

the channel cross section exceeded the capacity of a single 3-

L bottle, so water collected at each point in the cross section 

was poured into a Teflon-lined stainless steel churn splitter (a 

device for mixing and subsampling composite samples; 

Capel and Larson, 1996) and the individual glass sample 

bottles filled from the splitter.

At sites 13–17 and 20, grab samples were collected 

directly into glass sample bottles held at the end of a 

telescoping rod and submerged to a depth of approximately 1 

m while filling. The grab samples at sites 13, 14, and 15 were 

collected at the center of each channel from low bridges. 

Samples at site 16 were collected from the stream bank, and 

samples at sites 17 and 20 were collected from piers. At site 

21, subsurface grab samples were collected in glass bottles 

from Sacramento’s Tower Bridge using a weighted cage 

sampler suspended from a hand line and lowered from the 

water surface to the streambed while filling. 

Immediately after collection, samples were placed on 

wet ice in insulated coolers. Samples sent to the USGS’s 

National Water Quality Laboratory in Denver, Colorado, 

were shipped on ice by overnight freight on the day of 

collection. Samples collected for analysis by the California 

Department of Fish and Game Water Pollution Control 

Laboratory (CDFG laboratory) in Sacramento, California, 

were held in a refrigerated storage unit (4 degrees Celsius) 

until delivered to the lab at the end of each sampling event (1–

7 days holding time). Personnel handling sample collection 

bottles wore disposable latex or nitrile gloves. Teflon 

collection bottles and nozzles were rinsed three times in 

deionized water between samples. The collection bottles and 

the churn splitter used at sites 18 and 19 were field-washed 

with a nonphosphate detergent before rinsing with deionized 

water that had received additional treatment to remove 

organic compounds. Cleaned bottles, nozzles, and splitters 

were stored in clean polyethylene bags when not in use.

Laboratory Analytical Methods

The CDFG laboratory in Sacramento, California, 

analyzed samples from all sites with the exception of site 21. 

Gas chromatography coupled with an electron capture 

detector and thermionic specific detector (GC/ECD/TSD) 

was used to determine the concentration of diazinon, as well 

as chlorpyrifos, dimethoate, fonophos, malathion, 

methidathion, methyl parathion, and phosmet in 253 

environmental samples. Unfiltered samples were extracted 

with methylene chloride in a separatory funnel. The extract 

was dried with sodium sulfate, evaporated using a KudernaDanish apparatus, and solvent exchanged into petroleum 

ether. The extract was then concentrated using a microsnyder apparatus to about 1 ml and adjusted to 2 ml with isooctane before injection into the gas chromatograph. Tributyl 

phosphate and triphenyl phosphate were used as surrogates to 

evaluate the performance of the method. An optional florisil 

column cleanup procedure to eliminate or reduce 

interferences is part of the method’s Standard Operating 

Procedure (SOP), (Dave Crane, California Department of 

Fish and Game Water Pollution Control Laboratory, 

Sacramento, CA, written commun., 2001). For this method, 

the laboratory reporting limit for diazinon, chlorpyrifos, 

malathion, and methyl parathion concentration was 20 ng/L. 

The reporting limit for dimethoate, fonophos, methidathion, 

and phosmet was 50 ng/L.

At selected sites on the Sacramento and Feather Rivers 

where diazinon concentrations were expected to be below the 

CDFG laboratory detection limits, samples were analyzed by 

the USGS’s National Water Quality Laboratory (NWQL) in 

Denver, Colorado, using an analytical method with lower 

reporting limits. Duplicate (split-replicate) samples from 

sites 8, 18, and 20 were analyzed by both the CDFG and 

USGS laboratories. Samples collected at site 21 were 

analyzed only by the USGS laboratory. The USGS laboratory 

used gas chromatography with mass spectrometry (GC/MS) 

operated in the Selective Ion Monitoring (SIM) mode for 

identification and quantification of diazinon and 46 other 

pesticides and pesticide by-products. Water samples were 

filtered through baked glass fiber filters with a 0.7-μm 

effective pore diameter and organic compounds isolated by 

C–18 solid-phase extraction prior to analysis by GC/MS 

(Zaugg and others, 1995). The USGS lab reporting limit for 

diazinon concentration using this method was 5 ng/L.

Stage and Streamflow Measurement

Streamflow at seven sites (1, 4, 5, 8, 11, 20, and 21) was 

available from existing gaging stations. Sites 1, 4, and 11 

were located in proximity to active DWR gaging stations 

located at the Sacramento River at Hamilton City, Rose 

Avenue in Chico, and Butte Slough near Meridian, 

respectively. Site 8 was adjacent to a USGS gage at Colusa.

The DWR gage on Little Chico Creek at Taffee 

Avenue was used to estimate flow at site 5. The stream 

gage is located 3.5 mi downstream of the sampling site, 

and although there are no large tributaries between the 

gage and sample site, flow estimates for this site should 

be considered approximate. There were not enough 

data available to use flow routing methods to increase 

the reliability of estimates for this site. 
10 Occurrence and Transport of Diazinon, Sacramento River and Selected Tributaries, Calif., during Two Winter Storms, 2001

Streamflow at site 20 was estimated using records from 

a USGS gage at Verona located 8 mi upstream from the 

sampling site. Streamflow at site 21 was estimated using 

records at a USGS gage at Freeport 13 mi downstream of the 

sampling site. Because there is no significant inflow or 

outflow from the leveed channel between the stream gage and 

the sampling location at sites 20 and 21, and because the 

channel geometry is uniform throughout the intervening 

reach in both cases, flow estimates were based on time offsets 

between gage and sampling site calculated using Manning’s 

equation and mean stream velocity (Linsley and others, 

1958). Mean stream velocity used in the calculations was 

based on a stage-velocity relationship developed from 

previous discharge measurements made at the gage sites. 

Some flow data were available for site 3 from the DWR 

gage at Lindo Channel at Chico, but flow data at the time of 

sampling were missing during the monitoring period at that 

site. Data provided by DWR for Mud Creek at Chico (site 2) 

was limited to stage measurement. DWR was unable to make 

discharge measurements at the gage at the time of the study 

and did not calculate streamflow records for the site. A 

previously developed stage-discharge rating obtained from 

DWR was used to approximate streamflow at the site, but 

because channel conditions may have changed since the older 

rating was developed, the estimates must be considered only 

an approximation of streamflow at the time of sampling. 

Comparisons with streamflow measured downstream at Big 

Chico Creek near River Road indicate these approximations 

may be biased high.

Temporary stream gages were installed by the USGS at 

site 10 (Main Drainage Canal at Gridley Road) and site 16 

(Jack Slough near Doc Adams Road) to provide continuous 

streamflow data for the duration of the study. Streamflow 

records were developed by the USGS using continuous stage 

measurements recorded at the sites and instantaneous 

discharge measurements made by DPR staff (Rantz and 

others, 1982). Discharge measurements were made from 

bridges following USGS protocol using a type AA current 

meter suspended from a cable (Rantz and others, 1982). The 

gage at Jack Slough was located on Jack Slough Road 1 mi 

above the sampling site to avoid interference from fluctuating 

backwater conditions near the Feather River. Streamflow 

records at this site do not account for any local surface runoff 

between the gage and sampling site.

At selected sites where streamflow data were not 

available from gaging stations, discharge measurements were 

made at the time of sample collection. CSUC field crews 

measured discharge from a bridge at site 6 (Big Chico Creek 

at River Road) using a type AA current meter suspended from 

a cable. 

USGS field crews made wading measurements at site 19 

(Bear River near Berry Road) using a rod-suspended AA 

current meter (Rantz and others, 1982). On February 11 and 

12, the Bear River rose too high to safely wade. Streamflow 

at the time of sample collection on those two days was 

estimated from an extended stage-discharge rating curve 

developed using measurements made at wading stages (Rantz 

and others, 1982). A stage reference mark was installed at the 

site, and daily discharge measurements were made for several 

days after sample collection ended to provide additional data 

needed to develop a rating for the site. 

Measurements at site 18 (Feather River below Star 

Bend) were made by USGS field crews using an acoustic 

Doppler current profiler (ADCP) mounted on the sampling 

boat (Simpson, 2001). The ADCP measured the Doppler 

frequency shift of reflected sound waves (propagated by the 

instrument at a frequency of 1,200 kHz) to determine the 

speed and direction of moving water. Horizontal position and 

cross-section widths were determined using the bottomtracking function of the ADCP. Streamflow was calculated 

from ADCP data using the software program WinRiver from 

RD Instruments, Inc., the maker of the ADCP.

Only stage data were available from DWR gages at site 

9 (Butte Creek at Gridley Road), site 12 (Wadsworth Canal at 

South Butte Road), and site 17 (Feather River at Yuba City). 

Neither streamflow nor stage data were available for sites 7, 

13, 14, or 15. The closest stream gage to site 7 was 

approximately 21.5 mi upstream from the sampling site. 

Because inflow to the stream between the gage and the 

sampling site was unknown, the upstream gage could not be 

used to reliably estimate flow at the sampling site.

Sites 13, 14, and 15 were located just upstream of DWR 

pumping plants 1 and 2, which pump water into the Sutter 

Bypass when the water level in the leveed bypass is above the 

elevation of the surrounding land. Water levels in the bypass 

were low during the monitoring period, so flows in the 

channels leading to the pumping plants were attributed to 

gravity flow through gated culverts at the bypass with 

occasional pumping. Measurement of gravity flow was 

impractical because of the physical characteristics of the 

sites.
Study Design and Methodology 11

Load Calculation Methods

Instantaneous loads of diazinon were calculated by 

multiplying diazinon concentration by the streamflow at the 

time of sample collection with a unit conversion term. 

For example:

Concentration (ng/L)  Streamflow (ft3/s) 

5.3  10-6 = Load (lb/d)

Storm period loads were calculated for sites with a sufficient 

number of instantaneous load measurements to estimate the 

pattern of diazinon loading response (chemograph) over each 

of the two storm hydrographs monitored in the study.

Loading throughout each storm period was estimated for 

each 60-minute interval by linear interpolation between 

measured instantaneous loads in a simple spreadsheet model. 

Total loads for each storm period were calculated by 

summing the intervening hourly loads. This numerical 

estimation is functionally equivalent to estimating loads 

graphically from the measured area under a plot of load 

versus time. The same storm period was used for all sites 

upstream of Sacramento River at Tower Bridge. The two 

periods ran from January 24 at 9:00 a.m. to January 28 at 12 

p.m. and from February 9 at 9:00 a.m. to February 14 at 12 

p.m. Load estimates were often extrapolated a few hours past 

the first or last instantaneous measurement during the 

mornings of the first and last day so that the time period for 

load calculations were the same for all sites. Extrapolations 

were made using the observed trend in a graph of load against 

time for each site. 

Additional samples were collected by the USGS at 

Sacramento River at Tower Bridge (site 21) to extend the 

monitoring period at that site to January 31 for the first 

monitored storm period and to February 16 for the second 

period. Load values for the monitoring periods are presented 

in English units.

Quality Assurance and Quality Control

The reliability of field and laboratory methods used in 

this study was assessed by the analysis of blank, spiked, and 

replicate samples collected or prepared during environmental 

sampling trips. The comparability of data released from the 

two laboratories that provided analytical services for this 

study was evaluated from the results of split replicate samples 

sent to each laboratory. The results of the laboratory analysis 

of quality control samples are presented in appendix 1 (see 

back of report). 

Possible contamination of environmental samples from 

all sources, from collection and processing through 

laboratory analysis, was evaluated by analyzing field blanks. 

After cleaning the sampling equipment in the field, deionized 

water was passed through the sample collection bottles before 

being poured into sample bottles and stored alongside 

environmental samples. Seventeen such blanks were made at 

random times throughout the monitoring period. Eleven of 

these blanks were analyzed by the CDFG laboratory and six 

by the USGS laboratory. 

Ambient blanks were prepared by pouring deionized 

water directly into sample bottles at the same time that 

environmental samples were being processed in the field. 

These blanks were used to evaluate possible contamination 

from all sources except sampling equipment and collection 

bottles. Eleven ambient blanks were prepared at random 

times throughout the monitoring period and analyzed by the 

CDFG laboratory. No diazinon was detected in any field or 

ambient blank sample (Appendix 1, tables 1 and 4). Data 

from analysis of blank samples did not indicate any problem 

with site-to-site carryover of residual pesticides in sampling 

equipment or other possible sources of sample 

contamination. An estimated value of 1 ng/L of propanil, a 

post-emergent herbicide, was reported for one blank sample, 

a value that is far below the level of quantitation defined by 

the laboratory’s reporting level of 11 ng/L for this 

constituent. Values below the reporting level are also subject 

to an increased risk of false positive detection. Out of 43 

environmental samples analyzed by the USGS laboratory, 

only 4 estimated detections of propanil were noted. All four 

of these values were below the reporting limit and did not 

appear to be present in significant amounts in the 

environment or blank samples. 

The accuracy, or bias, of laboratory analyses was 

evaluated using spiked samples. Blind spikes were made by 

adding a known quantity of diazinon to split replicates of 

environmental samples before submitting them for analysis 

along with regular samples. In eight blind spikes analyzed by 

the CDFG laboratory, diazinon spike concentrations were set 

at 200 or 500 ng/L. Recovery ranged from 74 to 84 percent 

with a mean of 83 percent (Appendix 1, table 2). Two 

samples spiked with 100 ng/L of diazinon were submitted to 

the USGS laboratory. Recovery in these samples was 97 and 

111 percent (Appendix 1, table 5). Deviations from 100 

percent recovery represent bias and variability of laboratory 

methods as well as matrix effects caused by the interference 

of other organic materials that may be present in the samples.

The variability in each laboratory’s analytical results 

was evaluated by comparing diazinon concentrations in split 

replicate samples taken from the same water sample. Split 

replicates of 31 environmental samples were analyzed by the 

CDFG laboratory with concentrations ranging from reporting 

levels to 456 ng/L (Appendix 1, table 3). The mean relative 

percent difference between replicates above reporting levels 

(n = 18) was 7 percent (4 ng/L) with a standard deviation of 

21 percent (24 ng/L). Seven split replicates were analyzed by 

the USGS laboratory with concentrations ranging from 10 to 

100 ng/L (Appendix 1, table 4). The mean relative percent 

difference was 2 percent (0.4 ng/L) with a standard deviation 

of 8 percent (1.7 ng/L). 
12 Occurrence and Transport of Diazinon, Sacramento River and Selected Tributaries, Calif., during Two Winter Storms, 2001

Although the two laboratories that provided analytical 

services to the study used different methods, there was no 

measurable bias observed in the results reported by each 

laboratory. Because the CDFG laboratory used a method that 

extracted pesticides from whole water samples and the USGS 

laboratory used a method that extracted pesticides from 

filtered water samples, there was some concern that 

sediment-bound diazinon might be excluded from the USGS 

analysis resulting in lower concentration values. Bias in 

analytical results reported by the CDFG and USGS 

laboratories was evaluated using data from 30 split replicate 

environmental samples sent to both labs for concurrent 

analysis. Diazinon concentrations in 11 of these samples were 

above the reporting limits for both laboratories and ranged 

from 12 to 84 ng/L. The average difference in concentration 

reported by the two labs was 3 ng/L with a standard deviation 

of 9 ng/L. These differences are within the range of analytical 

variability observed during the study.

Concentrations in samples analyzed by the USGS 

laboratory were lower than the CDFG laboratory in only 4 of 

the 11 samples. In order to better compare results from the 

two laboratories, nine split replicates that were collected in 

the 2000 monitoring study and analyzed by both the CDFG 

and USGS laboratories using the same methods used in the 

current study (Dileanis and others, 2002) were included in 

this evaluation. The larger data set allows for a better 

statistical test for bias between the two labs. In the combined 

data set, diazinon concentrations in 6 of 20 samples analyzed 

by the USGS laboratory were lower than concentrations 

reported by the CDFG laboratory. A Wilcoxon signed rank 

test of the paired data did not show a statistically significant 

difference between the diazinon concentrations reported by 

the two labs (p = 0.13). On the basis of this interlaboratory 

comparison, there is no apparent bias between the methods 

employed by the two laboratories used in this study despite 

the use of filtered or whole water samples and other 

differences in methodology. Environmental concentrations of 

diazinon reported by the two laboratories and the load 

estimates derived from those concentrations are, therefore, 

directly comparable.

Hydrologic Conditions During the Study 

Period

Data from four National Weather Service gages in the 

Sacramento Valley were used to characterize rainfall in the 

study area during the 2000–2001 dormant spray season. 

These gages are located at Red Bluff in the north end of the 

valley, at Chico and Marysville in the mid-sections of the 

valley, and at Sacramento in the southern end of the valley. 

The average of the total rainfall from December 1, 2000, to 

March 31, 2001, at these gages was 12.3 in.

Total rainfall was slightly less than normal because of 

the lower-than-normal rainfall amounts in November and 

December. However, monthly rainfall for January was 13 

percent above normal, and for February was 47 percent above 

normal (fig. 3). Daily average rainfall at the four rain gages, 

and diazinon use, are shown in figure 4. 

Streamflow in the smaller tributaries in the valley 

generally reflects local storm runoff during the winter months 

after irrigation ends in autumn. Flows in the Sacramento, 

Feather, Yuba, and Bear Rivers are largely controlled by 

reservoirs above the valley floor. Releases from the upstream 

reservoirs are determined by downstream flood and reservoir 

management concerns and may not always correspond well 

to actual storm runoff patterns and rainfall amounts. Because 

there is relatively little agricultural land above the valley 

floor, releases from these reservoirs tend to dilute pesticides 

washed into the larger streams from sources in the valley. A 

relatively dry November and December left considerable 

storage capacity in the reservoirs, and flows in the 

Sacramento River and its regulated tributaries were relatively 

low compared with monthly mean flows and with conditions 

during the previous year’s diazinon monitoring study. The 

mean streamflow measured at Sacramento River at Verona 

(gage number 11425500 near site 20, Sacramento River at 

Alamar) for January and February 2001 was 52 and 54 

percent, respectively, of the mean monthly flows at that site 

since 1946 (after Shasta Dam became operational). The mean 

streamflow at Feather River at Oroville (gage number 

11407000, measuring releases from Lake Oroville to the 

Feather River) for January and February 2001 was 21 and 28 

percent, respectively, of mean monthly flows since 1969 

(after Oroville Dam became operational). The mean 

streamflow at Bear River near Wheatland (gage number 

11424000), just downstream of Camp Far West Reservoir, 

during January and February 2001 was less than 2 percent of 

the mean monthly flow since 1966 (Rockwell and others, 

2002).

Instantaneous streamflow at the time that samples were 

collected at Sacramento River at Alamar (site 20) in 2001 

ranged from 11,000 to 26,000 ft3/s. During the diazinon 

monitoring program’s 2000 sampling, instantaneous flows 

ranged from 32,600 to 62,300 ft3/s. At Feather River near 

Nicolaus, estimated flows (estimated by summing the flow at 

Feather River near Star Bend and the input from Bear River) 

ranged from 3,200 to 6,400 ft3/s in 2001. In 2000, flows 

ranged from 5,900 to 41,100 ft3/s. Flows measured or 

estimated in the Bear River at the time of sample collection 

were between 77 and 855 ft3/s in 2001 and between 1,030 and 

17,400 ft3/s in 2000.
Hydrologic Conditions During the Study Period 13

0

1

2

3

4

5

6

July Aug. Sept. Oct. Nov. Dec. Jan. Feb. Mar. Apr. May June

Monthly rainfall, in inches

2000–2001

Normal

2000 2001

Figure 3. Monthly rainfall in the Sacramento Valley, California. 

Values are the average of rainfall recorded at Red Bluff, Chico, Marysville, and Sacramento. Normal values represent average monthly rainfall from 1961 to 

1990 for the four sites. Source: National Oceanic and Atmospheric Administration, 2001.

0

0.5

1

Daily rainfall in inches

0

500

1,000

1,500

2,000

2,500

3,000

3,500

4,000

Diazinon use, in pounds a.i.

Storm monitoring period

Diazinon use

Rainfall

Dec. Jan. Feb. Mar.

2000 2001

Figure 4. Daily rainfall and reported diazinon use in the Sacramento Valley, California, during the 2000–2001 dormant spray season. 

Rainfall values are the average of values recorded at weather stations in Red Bluff, Chico, Marysville, and Sacramento. Diazinon use data were derived 

from the California Department of Pesticide Regulation's Pesticide Use Database for areas in the valley draining to the Sacramento River upstream of 

Sacramento. Shaded areas identify sample collection periods. (a.i., active ingredient). 
14 Occurrence and Transport of Diazinon, Sacramento River and Selected Tributaries, Calif., during Two Winter Storms, 2001

Occurrence and Transport of Diazinon

Diazinon Use in the Sacramento Valley

In California, state regulations require that the location 

and quantity of agricultural and commercial pesticide 

applications must be reported to DPR. That information is 

compiled in the agency’s Pesticide Use Database and 

released as a Pesticide Use Report (PUR) each year. 

The quantity of diazinon applied to agricultural lands in 

the Sacramento Valley during dormant spray seasons from 

1993 to 2001 is presented in figure 5. Diazinon use decreased 

during that period. In the 1999–2000 and 2000–2001 seasons, 

42,400 and 40,700 lb a.i. (pounds active ingredient) were 

applied to agricultural lands compared with over 80,000 lb 

a.i. four years earlier. The decrease may be due in part to 

lower market prices for orchard crops and changes in 

management practices, including the substitution of other 

insecticides, such as pyrethrins, for diazinon (Epstein and 

others, 2001).

The greatest diazinon use occurs in January and 

February. During the last eight dormant spray seasons, 59 

percent of the total use on the valley floor was in January and 

27 percent in February (statistics derived from the Pesticide 

Use Database, California Department of Pesticide 

Regulation, 2002).

Bar charts and maps in figures 6 through 13 show daily 

diazinon use and the location of applications during the 

2000–2001 dormant spray season in subbasins upstream of 

selected sampling sites. Maps and subbasin use data were 

developed from a GIS coverage of the study area that 

incorporated data from the Pesticide Use Database. Locations 

are given at the section level of the Public Lands Survey 

System. Only those subbasins with known boundaries could 

be included in the GIS analysis. 

The general timing of applications throughout the 2001 

dormant spray season (December 1 to March 31) can be seen 

in figure 6A. This figure shows all applications in the 

watershed that drains to the Sacramento River upstream of 

Sacramento River at Tower Bridge (site 21). Diazinon 

applications in the part of the valley draining to the Colusa 

Basin Drain are not included in the figure because the drain is 

diverted to the Yolo Bypass and the delta during winter 

months and does not flow into the Sacramento River. Large 

scale diazinon applications began in mid- December, and by 

February 5, 86 percent of the seasonal applications had been 

applied.

Pesticide applications upstream of monitoring sites with 

defined drainage boundaries during four time periods related 

to the monitored storm events are summarized in table 2. 

Period 1 includes all early season applications from 

December 1 through 23. Period 2 includes all applications 

made in the 30 days prior to the first sample collection on 

January 24. Period 3 includes applications made after the first 

monitored storm until the second monitored storm. Period 4 

covers the time between the last monitored storm and the end 

of the dormant spray season. Rainfall did occur during period 

4. However, only 14 percent of the total diazinon application 

of the dormant spray period occurred during period 4.

Figure 5. Diazinon use in the Sacramento Valley, California, during dormant spray seasons from 1993 to 2001.

[Data derived from California Department of Pesticide Regulation, Pesticide Use Database].

Diazinon use in the Sacramento Valley

20,000

0

40,000

60,000

80,000

100,000

1993_94 1994_95 1995_96 1996_97 1997_98 2000_ 1999 2001 _ 1998 2000 _99

Dormant spray season

Diazinon, in pounds active ingredient

March

February

January

December
Occurrence and Transport of Diazinon 15

Diazinon, in pounds active ingredient

0

500

1,000

1,500

2,000

Dec. Jan. Feb. Mar.

2000 2001

Sacramento River at Tower Bridge

Figure 6. Diazinon use upstream of Sacramento River at Tower Bridge (site 21). 

(A) Daily diazinon use from December 1, 2000, to March 31, 2001. 

See figure 1 and table 1 for site location.
16 Occurrence and Transport of Diazinon, Sacramento River and Selected Tributaries, Calif., during Two Winter Storms, 2001

0 10 20 MILES

0 10 20 KILOMETERS

Stony Creek

<46

46–149

>149

Diazinon use (pounds applied, a.i.)

Subbasin boundary

Sampling site

Valley floor

39

30

12230 12212130 121

39

40

Big

Chico

Creek

Sacramento River

Feather River

Figure 6. Diazinon use upstream of Sacramento River at Tower Bridge (site 21). 

(B) Areal distribution of applications. 

See figure 1 and table 1 for site location. [<, less than; >, greater than; a.i., active ingredient].
Occurrence and Transport of Diazinon 17

Sacramento River at Alamar

Diazinon, in pounds active ingredient

0

500

1,000

1,500

2,000

Dec. Jan. Feb. Mar.

2000 2001

Figure 7. Diazinon use upstream of Sacramento River at Alamar (site 20). 

(A) Daily diazinon use from December 1, 2000, to March 31, 2001. 

See figure 1 and table 1 for site location. 
18 Occurrence and Transport of Diazinon, Sacramento River and Selected Tributaries, Calif., during Two Winter Storms, 2001

Stony Creek

Sacramento River

Feather River

Big

Chico

Creek

0 10 20 MILES

0 10 20 KILOMETERS

12230 12212130 121

39

30

39

40

<46

46–149

>149

Diazinon use (pounds applied, a.i.)

Subbasin boundary

Sampling site

Valley floor

Figure 7. Diazinon use upstream of Sacramento River at Alamar (site 20). 

(B) Areal distribution of applications.

See figure 1 and table 1 for site location. [<, less than; >, greater than; a.i., active ingredient]
Occurrence and Transport of Diazinon 19

Bear River near Berry Road

Diazinon, in pounds active ingredient

0

100

200

300

400

Dec. Jan. Feb. Mar.

1999 2000

Figure 8. Diazinon use upstream of Bear River near Berry Road (site 19). 

(A) Daily diazinon use from December 1, 1999, to March 30, 2000. 

See figure 1 and table 1 for site location. 
20 Occurrence and Transport of Diazinon, Sacramento River and Selected Tributaries, Calif., during Two Winter Storms, 2001

0 5 10 METERS

0 5 10 KILOMETERS

<46

46–149

>149

Diazinon use (pounds applied, a.i.)

Subbasin boundary

Sampling site

Valley floor

12130

39

07

39

12137 12122

EXPLANATION

Bear River

Feather River

Figure 8. Diazinon use upstream of Bear River near Berry Road (site 19). 

(B) Areal distribution of applications. 

See figure 1 and table 1 for site location. [<, less than; >, greater than; a.i., active ingredient].
Occurrence and Transport of Diazinon 21

Diazinon, in pounds active ingredient

1,000

800

600

400

200

0

Dec. Jan. Feb. Mar.

1999 2000

Feather River below Star Bend

Figure 9. Diazinon use upstream of Feather River below Star Bend (site 18). 

(A) Daily diazinon use from December 1, 1999, to March 30, 2000. 

See figure 1 and table 1 for site location.
22 Occurrence and Transport of Diazinon, Sacramento River and Selected Tributaries, Calif., during Two Winter Storms, 2001

<46

46–149

>149

Diazinon use (pounds applied, a.i.)

Subbasin boundary

Sampling site

Valley floor

EXPLANATION

12137

39

15

39

07

39

12130

0 2.5 5 MILES

0 2.5 5 KILOMETERS

Honcut Creek

Feather River

Yuba River

Jack Slough

Figure 9. Diazinon use upstream of Feather River below Star Bend (site 18). 

(B) Areal distribution of applications. 

See figure 1 and table 1 for site location. [<, less than; >, greater than; a.i., active ingredient]
Occurrence and Transport of Diazinon 23

Jack Slough near Doc Adams Road

Diazinon, in pounds active ingredient

400

300

200

100

0

Dec. Jan. Feb. Mar.

1999 2000

<46

46–149

>149

Diazinon use (pounds applied, a.i.)

Subbasin boundary

Sampling site

Valley floor

EXPLANATION

12137 12130

39

15

39

07

Jack Slough

Honcutt Creek

Yuba River

0 2.5 5 KILOMETERS

0 2.5 5 MILES

Figure 10. Diazinon use upstream of Jack Slough near Doc Adams Road (site 16). 

(B) Areal distribution of applications. 

See figure 1 and table 1 for site location. [<, less than; >, greater than; a.i., active ingredient]

Figure 10. Diazinon use upstream of Jack Slough near Doc Adams Road (site 16). 

(A) Daily diazinon use from December 1, 1999, to March 30, 2000. 

See figure 1 and table 1 for site location.
24 Occurrence and Transport of Diazinon, Sacramento River and Selected Tributaries, Calif., during Two Winter Storms, 2001

Main Drainage Canal at Gridley Road

Diazinon, in pounds active ingredient

400

300

100

200

0

Dec. Jan. Feb. Mar.

1999 2000

Sutter

Buttes

0 5 10 MILES

0 10 KILOMETERS

<46

46–149

>149

Diazinon use (pounds applied, a.i.)

Subbasin boundary

Sampling site

Valley floor

EXPLANATION

12152 12145 12137 39

30

39

22

39

15

Main

Drainage Canal

Butte Creek

Feather River

Figure 11. Diazinon use upstream of Main Drainage Canal at Gridley Road (site 10). 

(A) Daily diazinon use from December 1, 1999, to March 30, 2000.

See figure 1 and table 1 for site location.

Figure 11. Diazinon use upstream of Main Drainage Canal at Gridley Road (site 10). 

((B) Areal distribution of applications. 

See figure 1 and table 1 for site location. [<, less than; >, greater than; a.i., active ingredient] 
Occurrence and Transport of Diazinon 25

Diazinon, in pounds active ingredient

0

200

400

600

800

1,000

Dec. Jan. Feb. Mar.

1999 2000

Butte Creek at Gridley Road

Figure 12. Diazinon use upstream of Butte Creek at Gridley Road (site 9). 

(A) Daily diazinon use from December 1, 1999, to March 30, 2000.

See figure 1 and table 1 for site location.
26 Occurrence and Transport of Diazinon, Sacramento River and Selected Tributaries, Calif., during Two Winter Storms, 2001

39

30

39

22

39

37

12212152 12145

Sacramento River

Butte Creek

0 5 MILES 2.5

0 5 KILOMETERS 2.5

<46

46–149

>149

Diazinon use (pounds applied, a.i.)

Subbasin boundary

Sampling site

Valley floor

Figure 12. Diazinon use upstream of Butte Creek at Gridley Road (site 9). 

(B) Areal distribution of applications. 

See figure 1 and table 1 for site location. [<, less than; >, greater than; a.i., active ingredient]
Occurrence and Transport of Diazinon 27

Sacramento River at Colusa

Diazinon, in pounds active ingredient

2,000

1,000

1,500

500

0

Dec. Jan. Feb. Mar.

1999 2000

Figure 13. Diazinon use upstream of Sacramento River at Colusa (site 8). 

(A) Daily diazinon use from December 1, 1999, to March 30, 2000. 

See figure 1 and table 1 for site location. 
28 Occurrence and Transport of Diazinon, Sacramento River and Selected Tributaries, Calif., during Two Winter Storms, 2001

Big

Chico Creek

Stony Creek

<46

46–149

>149

Diazinon use (pounds applied, a.i.)

Subbasin boundary

Sampling site

Valley floor

0 10 20 MILES

0 10 20 KILOMETERS

12130 122

40

39

30

Sacramento River

Figure 13. Diazinon use upstream of Sacramento River at Colusa (site 8). 

(B) Areal distribution of applications. 

See figure 1 and table 1 for site location. [<, less than; >, greater than; a.i., active ingredient]
Occurrence and Transport of Diazinon 29

Table 2. Diazinon use in selected subbasins during four time periods in the 2000–2001 dormant spray season, Sacramento Valley, California. 

[Pounds applied are active ingredient. Subbasin area and area applied are in square miles. Colusa Basin Drain was not a study site but is included for 

comparison] 

Site name Basin area

Period 1 

(12/1/00-12/23/00)

Period 2 

(12/24/00-1/24/01)

Pounds

applied

Area applied 

(in basin)

Pounds

applied

Area applied 

(in basin)

Bear River near Berry Road 574 344 1.0 169 1.5

Butte Creek at Gridley Road 589 180 1.0 1,010 7.4

Main Drainage Canal at Gridley Road 35 0 0 386 4.1

Jack Slough near Doc Adams Road 73 321 3.8 1,122 6.9

Feather River below Star Bend 5,300 442 5.9 2,987 14

Feather River at Yuba City 3,940 430 5.7 2,323 11

Sacramento River at Colusa 12,260 125 2.9 3,234 22

Sacramento River at Alamar 19,810 3,114 33 19,105 124

Sacramento River at Tower Bridge 22,020 3,114 33 19,111 127

Colusa Basin Drain (for comparison) 1,630 0 0 4,126 32

Site name Basin area

Period 3 

(1/25/01-2/09/01)

Period 4 

(2/10/001-

3/31/01) Total pounds 

applied

Pounds

applied

Area applied 

(in basin)

Pounds

applied

Area applied 

(in basin)

Bear River near Berry Road 574 139 1.0 0 0.0 653

Butte Creek at Gridley Road 589 511 3.3 0 0.0 1,701

Main Drainage Canal at Gridley Road 35 137 1.3 680 2.9 1,203

Jack Slough near Doc Adams Road 73 119 2.0 70 0.6 1,631

Feather River below Star Bend 5,300 257 5.0 104 2.4 3,790

Feather River at Yuba City 3,940 206 4.2 104 2.4 3,062

Sacramento River at Colusa 12,260 3,806 21 2,412 36 9,577

Sacramento River at Alamar 19,810 7,029 61 4,553 58 33,801

Sacramento River at Tower Bridge 22,020 7,041 63 4,567 62 33,832

Colusa Basin Drain (for comparison) 1,630 1,549 13 416 8.2 6,091
30 Occurrence and Transport of Diazinon, Sacramento River and Selected Tributaries, Calif., during Two Winter Storms, 2001

Concentrations of Diazinon Observed during Storms

Diazinon concentrations measured at many of the 

sampling sites are plotted together with stream discharge in 

figure 14 or with stage (if no discharge was available) in 

figure 15. Sites with few or no detections were not included. 

The results of all laboratory analyses and field measurements 

are presented in appendix 2 (see back of report). With a few 

exceptions, the highest diazinon concentrations were 

observed during the first of the two monitored storms. The 

median concentration was 55 ng/L in samples collected 

during the first storm and 26 ng/L during the second storm. A 

similar pattern was observed in the 1999–2000 monitoring 

study where concentrations declined in each of the three 

successive storms monitored in that study (Dileanis and 

others, 2002). The two notable exceptions to this trend in the 

2000–2001 study were at the Main Drainage Canal at Gridley 

Road (site 10) and Wadsworth Canal at South Butte Road 

(site 12). Higher concentrations during the second storm at 

these sites may have been related to the timing of applications 

and to the length of time for transport from points of 

application to sampling sites in the slow moving drains. 

Diazinon use in the Main Drainage Canal watershed was 

more evenly distributed throughout the season than in the 

other subbasins. However, a greater amount of diazinon was 

applied before the first monitored storm than in the interval 

between the first and second storms. Diazinon transport from 

points of application to the sampling site may be slower than 

in many of the other subbasins in the study area, resulting in 

a greater time lag between the onset of rainfall and the 

appearance at the sampling site. The Main Drainage Canal at 

Gridley Road site showed the same trend of higher 

concentrations in later storms during the previous dormant 

spray season. Because the watershed boundaries of the 

Wadsworth Canal were not known, the timing of diazinon 

applications upstream of the sampling site could not be 

determined. 

0

20

40

60

80

100

120

23 24 25 26 27 28 29 30 31 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17

Diazinon concentration, in nanograms per liter

0

6,000

12,000

18,000

24,000

30,000

36,000

Discharge, in cubic feet per second

Diazinon

Discharge

Sacramento River at Tower Bridge

Jan. Feb.

2000

Figure 14. Diazinon concentrations and streamflow at sampling sites in the Sacramento Valley, California, from January 23, 2000, to February 17, 2001. 

(A) Sacramento River at Tower Bridge (site 21). 

See figure 1 and table 1 for location.
Occurrence and Transport of Diazinon 31

0

6,000

12,000

18,000

24,000

30,000

36,000

Discharge, in cubic feet per second

Diazinon

Discharge

Sacramento River at Alamar

0

20

40

60

80

100

120

Diazinon concentration, in nanograms per liter

23 24 25 26 27 28 29 30 31 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16

Jan. Feb.

2000

Figure 14. Diazinon concentrations and streamflow at sampling sites in the Sacramento Valley, California, from January 23, 2000, to February 17, 2001. 

(B) Sacramento River at Alamar (site 20). 

See figure 1 and table 1 for location.
32 Occurrence and Transport of Diazinon, Sacramento River and Selected Tributaries, Calif., during Two Winter Storms, 2001

0

100

200

300

400

500

600

700

800

900

Discharge, in cubic feet per second

23 24 25 26 27 28 29 30 31 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16

Jan. Feb.

2000

0

20

10

40

30

60

50

80

70

Diazinon concentration, in nanograms per liter

Diazinon

Discharge

Bear River near Berry Road

Figure 14. Diazinon concentrations and streamflow at sampling sites in the Sacramento Valley, California, from January 23, 2000, to February 17, 2001. 

(C) Bear River near Berry Road (site 19). 

See figure 1 and table 1 for location.
Occurrence and Transport of Diazinon 33

0

1,000

2,000

3,000

4,000

5,000

6,000

Discharge, in cubic feet per second

Diazinon

Discharge

Feather River below Star Bend

80

70

60

50

40

30

20

10

0

Diazinon concentration, in nanograms per liter

23 24 25 26 27 28 29 30 31 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16

Jan. Feb.

2000

Figure 14. Diazinon concentrations and streamflow at sampling sites in the Sacramento Valley, California, from January 23, 2000, to February 17, 2001. 

(D) Feather River below Star Bend (site 18). 

See figure 1 and table 1 for location.
34 Occurrence and Transport of Diazinon, Sacramento River and Selected Tributaries, Calif., during Two Winter Storms, 2001

0

20

40

60

80

100

120

140

0

40

80

120

160

200

240

280

23 24 25 26 27 28 29 30 31 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16

Jan. Feb.

2000

Discharge, in cubic feet per second

Diazinon concentration, in nanograms per liter

Diazinon

Discharge

Jack Slough near Doc Adams Road

Figure 14. Diazinon concentrations and streamflow at sampling sites in the Sacramento Valley, California, from January 23, 2000, to February 17, 2001. 

(E) Jack Slough near Doc Adams Road (site 16). 

See figure 1 and table 1 for location.
Occurrence and Transport of Diazinon 35

0

10

20

30

40

50

60

70

80

23 24 25 26 27 28 29 30 31 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16

0

200

400

600

800

1,000

1,200

1,400

1,600

Discharge, in cubic feet per second

Diazinon concentration, in nanograms per liter

Diazinon

below RL

Discharge

Butte Slough at Lower Pass Road

Jan. Feb.

2000

Figure 14. Diazinon concentrations and streamflow at sampling sites in the Sacramento Valley, California, from January 23, 2000, to February 17, 2001. 

(F) Butte Slough at Lower Pass Road (site 11). 

See figure 1 and table 1 for location. RL, reporting limit.
36 Occurrence and Transport of Diazinon, Sacramento River and Selected Tributaries, Calif., during Two Winter Storms, 2001

0

20

40

60

80

100

120

140

160

180

200

23 24 25 26 27 28 29 30 31 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16

0

50

100

150

200

250

Jan. Feb.

2000

Diazinon concentration, in nanograms per liter

Discharge, in cubic feet per second

Diazinon

Discharge

Main Drainage Canal at Gridley Road

Figure 14. Diazinon concentrations and streamflow at sampling sites in the Sacramento Valley, California, from January 23, 2000, to February 17, 2001. 

(G) Main Drainage Canal at Gridley Road (site 10). 

See figure 1 and table 1 for location.
Occurrence and Transport of Diazinon 37

0

20

40

60

80

100

23 24 25 26 27 28 29 30 31 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16

0

5,000

10,000

15,000

20,000

25,000

Diazinon concentration, in nanograms per liter

Discharge, in cubic feet per second

Jan. Feb.

2000

Diazinon

below RL

Discharge

Sacramento River at Colusa

Figure 14. Diazinon concentrations and streamflow at sampling sites in the Sacramento Valley, California, from January 23, 2000, to February 17, 2001. 

(H) Sacramento River at Colusa (site 8). 

See figure 1 and table 1 for location. RL, reporting limit.
38 Occurrence and Transport of Diazinon, Sacramento River and Selected Tributaries, Calif., during Two Winter Storms, 2001

0

200

400

600

800

1,000

1,200

1,400

1,600

36.5

37

37.5

38

38.5

39

39.5

40

40.5

Stage, in feet

Diazinon

Stage

Wadsworth Canal at South Butte Road

24 25 26 27 28 29 30 31 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16

Jan. Feb.

2000

Diazinon concentration, in nanograms per liter

Figure 15. Diazinon concentrations and stream stage at sampling sites in the Sacramento Valley, California, from January 23, 2000, to February 16, 2001. 

(A) Wadsworth Canal at South Butte Road (site 12). 

See figure 1 and table 1 for location. 
Occurrence and Transport of Diazinon 39

0

20

40

60

80

100

23 24 25 26 27 28 29 30 31 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16

0.0

2.0

4.0

6.0

8.0

10.0

Stage, in feet

Jan. Feb.

2001

Butte Creek at Gridley Road

Diazinon

below reporting limit

Stage

Diazinon concentration, in nanograms per liter

Figure 15. Diazinon concentrations and stream stage at sampling sites in the Sacramento Valley, California, from January 23, 2000, to February 16, 2001. 

(B) Butte Creek at Gridley Road (site 9) from January 23, 2000, to February 16, 2001.

See figure 1 and table 1 for location. 
40 Occurrence and Transport of Diazinon, Sacramento River and Selected Tributaries, Calif., during Two Winter Storms, 2001

Peak concentrations often coincided with peak storm 

flows. Exceptions to this pattern can be observed at Butte 

Creek at Gridley Road (site 9), Feather River below Star 

Bend (site 18), and Jack Slough near Doc Adams Road 

(site 16). Peak concentrations at these sites occurred prior to 

or after peak flows. These patterns may be due to dilution of 

local agricultural runoff with flows originating upstream of 

agricultural areas. Despite the proximity of agricultural land 

to the monitoring sites, the flat topography of the valley floor 

(and the resulting low velocities in many of the channels 

draining that area) may result in significant lag times in 

transport of diazinon from points of application to the 

monitoring sites.

Boxplots of diazinon concentration during the 

monitoring period at many of the sites are shown in figure 16. 

Sites with few samples or few concentrations above reporting 

levels are not included. Sites receiving mostly agricultural or 

urban drain water had the highest concentrations of diazinon. 

Samples collected at Wadsworth Canal at South Butte Road 

(site 12), which drains agricultural lands east of the Sutter 

Buttes, had a median concentration of 308 ng/L and a 

maximum value of 1,380 ng/L. These were the highest values 

observed during the monitoring period. Other drains with 

relatively high concentrations were DWR Pump Plant 1 (site 

15), Jack Slough near Doc Adams Road (site 16), Main 

Drainage Canal at Gridley Road (site 10), DWR Pump Plant 

2–north channel (site 13), and DWR Pump Plant 2–south 

channel (site 14), with median concentrations of 141, 78, 68, 

61, and 50 ng/L, respectively. 

Diazinon concentrations were lower in samples 

collected at sites draining medium-sized basins where 

agricultural land occupies a smaller percentage of the 

watershed. Median concentrations at Bear River near Berry 

Road (site 19), Butte Slough at Lower Pass Road (site 11), 

and Butte Creek at Gridley Road (site 9) were 43, 29, and 28 

ng/L, respectively. The lowest concentrations observed were 

at the large river sites where most of the flow originated in 

nonagricultural and nonurban land. Median concentrations at 

Sacramento River at Colusa (site 8) and Feather River above 

Star Bend were both 15 ng/L. The median concentration at 

Sacramento River at Alamar (site 20), which is downstream 

of most agricultural inputs, was 21 ng/L. The median 

concentration at Sacramento River at Tower Bridge (site 21), 

which receives drainage from the northern portion of the 

Sacramento metropolitan area in addition to upstream 

agricultural inputs, was very similar at 20 ng/L.

1

10

100

1,000

10,000 Diazinon concentration, in nanograms per liter

n=10 41 40 11 33 10 10 10 9 10 10 11 12

8 9 10 11 12 13 14 15 16 18 19 20 21

Site number

Figure 16. Boxplots of diazinon concentrations at many of the sampling sites in the Sacramento Valley, California. 

[μg/L, microgram per liter. Values less than the reporting limit set at 1/2 reporting limit for the following sites: 8 (1/2 reporting limit = 2.5 μg/L), 9, 11, and 14 

(1/2 reporting limit =10 μg/L).]
Occurrence and Transport of Diazinon 41

During the second monitored storm, samples were 

collected at Sacramento River at Hamilton City (site 1), 

Stony Creek at Highway 45 (site 7), and in streams receiving 

urban storm runoff from the city of Chico. All diazinon 

concentrations at Sacramento River at Hamilton City (site 1) 

were below the reporting limit (20 ng/L) for the method used 

at that site. Samples collected at Stony Creek at Highway 45 

(site 7) were near or below the reporting limit of 20 ng/L. 

Samples collected from Mud Creek at Chico (site 2), Lindo 

Channel at Chico (site 3), and Little Chico Creek (site 5) had 

values ranging from 20 to 185 ng/L. Samples were collected 

from two sites on Big Chico Creek (sites 4 and 6), which 

originates in the Sierra foothills and runs through the city of 

Chico before discharging into the Sacramento River. 

Diazinon concentrations at Big Chico Creek at Chico (site 4) 

ranged from below the reporting limit to 24 ng/L. Diazinon 

concentrations in seven of the nine samples collected at Big 

Chico Creek at River Road (site 6), located farther 

downstream, were below the laboratory reporting limit of 20 

ng/L. Concentrations in the two samples above the reporting 

limit were 22 and 62 ng/L.

Rain from the first monitored storm occurred from 

January 23 to 26 and produced an average total rainfall of 1.9 

in. at the four rain gages mentioned earlier. An earlier large 

storm, which began on January 7, produced an average total 

rainfall of 2.9 in. The January 7 storm was not monitored, 

because it was believed at the time that few dormant spray 

applications had been made before that date. However, data 

from the PUR released the following year show that 34 

percent (11,900 lb a.i.) of the total seasonal diazinon 

applications were made in the 30 days prior to the storm. One 

of the difficulties in carrying out storm runoff studies of 

pesticide transport is choosing the most relevant storms to 

monitor, given a limited number of samples that can be 

collected and the limited information available about the 

amount and timing of recent pesticide applications in an area 

as large as the Sacramento Valley.

Diazinon applications between the January 7 storm and 

the first monitored storm were 32 percent (11,300 lb a.i.) of 

the season total. Although the “first flush’ of the January 7 

storm was missed, the pre-storm applications for both storms 

were similar in quantity and timing. The amounts of diazinon 

transported to the aquatic environment during both storms 

may have been similar. 

The average rainfall during the second monitored storm 

(1.6 in.) was slightly less than the rainfall during the first 

monitored storm, and less diazinon was applied in the valley 

during the dry period before the second storm (7,300 lb a.i. or 

21 percent of the season total) than was applied during the dry 

period before the first monitored storm. These two factors 

may explain the lower concentrations observed overall during 

the second monitored storm.

Two major storms occurred after the monitoring ended 

at most sites on February 14 (fig. 4). Less than 6 percent 

(4,600 lb a.i.) of the seasonal total was applied in the dry 

period just before those storms, and resulting diazinon 

concentrations were probably considerably less than the 

earlier monitored storms.

Because reservoir releases were relatively low during 

the 2001 monitoring period, diazinon transported to the 

Sacramento and Feather Rivers from storm runoff on the 

valley floor was less likely to be diluted by upstream flows 

originating in nonagricultural areas. Concentrations in these 

large rivers during years with higher rainfall and larger storm 

releases from upstream reservoirs may be lower given similar 

diazinon use.

Measured and Estimated Diazinon Loads at 

Monitoring Sites

Storm period loads were estimated for sites 8, 10, 11, 16, 

18, 19, 20, and 21 during the two monitoring periods 

(table 3). The estimated load at Sacramento River at Tower 

Bridge (site 21) for both periods was 52 lb. Because there 

were no diversions from the Sacramento River to the Yolo 

Bypass during the monitoring period, this load represents the 

sum of all sources in the Sacramento Valley with the 

exception of the Colusa Basin Drain watershed, which is 

diverted to the Bypass through the Knights Landing Ridge 

Cut each winter. Loads at the Sacramento River at Colusa 

(site 8) during the two 5-day monitoring periods represent 

about 30 percent of the loads at Tower Bridge. Because the 

5-day length of the monitoring periods at these two sites did 

not include all the high flows from runoff, the time periods for 

load estimation at the Sacramento River at Colusa were 

extended two additional days beyond the time of the last 

sample collection to include most of the storm runoff that 

passed through the site. Diazinon concentrations during the 

additional two days were estimated graphically by extending 

the decreasing trends in concentration observed during the 

last days of the monitoring period and using the site 

hydrograph as a guide to runoff conditions. The percent of the 

storm load at Tower Bridge originating upstream of Colusa 

did not change significantly (34 percent) using the estimated 

full storm runoff period.
42 Occurrence and Transport of Diazinon, Sacramento River and Selected Tributaries, Calif., during Two Winter Storms, 2001

Loads from the Feather River were estimated by 

summing loads at Feather River below Star Bend (site 18) 

and Bear River near Berry Road (site 19). Approximately 6.2 

lb of diazinon was estimated to have entered the Sacramento 

River from the Feather River during the monitoring periods, 

representing about 12 percent of the load at Sacramento River 

at Tower Bridge (site 21). This is about half the percentage 

estimated for the Feather River during the previous dormant 

spray season (Dileanis and others, 2002).

Several problems were encountered in developing load 

estimates for creeks draining the Chico urban area, and load 

estimates are only available for the second storm-monitoring 

period in February. In Little Chico Creek, discharge was not 

reported by DWR for the Taffee Avenue Gage during the 

period just before samples were collected. The reliability of 

data from the gage during the times of sample collection was 

uncertain, thus reducing the confidence of the estimated 

loading of 0.04 lb, which is based on the two samples 

collected at the site.

The discharge record at the Lindo Channel at Chico gage 

(site 3) was limited in that there were data gaps during the 

monitoring period. Instantaneous streamflow measurements 

were made at the time of sample collection at the Lindo 

Channel at Chico (site 3), and instantaneous loads of 0.004 

lb/d and 0.028 lb/d were estimated. These loads, coupled with 

visual observations of low flows in the channel throughout 

the storm period, suggest that the total load would have been 

small and comparable to loads estimated for Little Chico 

Creek. 

Loads from Mud Creek during the monitoring period 

were estimated to be 0.11 lb on the basis of the two samples 

and a continuous discharge record. Because the discharge 

record for this site may be overestimated, the load estimate 

may be conservatively high. Only two of the nine samples 

collected at Big Chico Creek at Chico (site 4) were above the 

laboratory reporting limit of 20 ng/L. On the basis of this 

limited data, the load estimate for the second monitoring 

period is 0.04 lb. Diazinon concentrations at Big Chico Creek 

at River Road (site 6) were also below the reporting limit for 

seven of the nine samples collected. Only instantaneous 

streamflow measurements made at the time of sampling were 

available for this site. Instantaneous load estimates of 0.02 

and 0.1 lb/d were made for the two occasions when samples 

with concentrations above reporting limits were collected.

Loads from Wadsworth Canal at South Butte Road 

(site12), the DWR pumping plants (sites 13–15), Butte Creek 

at Gridley Road (site 9), Feather River at Yuba City (site 17), 

and Stony Creek at Highway 45 (site 7) could not be 

estimated because no streamflow data were available for 

these sites. Loads at Sacramento River at Hamilton City (site 

1) could not be estimated because diazinon concentrations at 

this site were below the laboratory reporting limits (20 ng/L) 

in all five samples collected at the site.

Estimated loads from the Sacramento River upstream of 

Colusa, the Feather River, and Butte Slough (which includes 

Butte Creek) upstream of the Sutter Bypass made up about 40 

percent of the load estimated at Sacramento River at Tower 

Bridge (site 21). A significant portion of the diazinon load 

measured at Sacramento River at Tower Bridge may have 

originated from sources draining into the Sutter Bypass, for 

which no load estimates are available. About half 

(approximately 16,800 lb) of the diazinon that was applied in 

the 2001 dormant spray season was used in this area, which 

is east and southeast of the Sutter Buttes and drains to the 

Sutter Bypass through the Wadsworth Canal and at the DWR 

pumping plants. 

Table 3. Diazinon loads estimated for sites in the Sacramento Valley, California, during two storm-monitoring periods in 2001. 

[All values are in pounds]

Site 

number Site name Storm monitoring

period 1 

Storm monitoring

period 2 Total

8 Sacramento River at Colusa 12.5 2.68 15.1

10 Main Drainage Canal at Gridley Road 0.22 0.26 0.48

11 Butte Slough at Lower Pass Road 0.86 0.57 1.43

16 Jack Slough near Doc Adams Road 0.28 0.36 0.64

18 Feather River below Star Bend 1.54 0.34 1.87

19 Bear River near Berry Road 0.22 0.40 0.62

20 Sacramento River at Alamar 16.4 8.72 25.1

21 Sacramento River at Tower Bridge (5 days) 18.9 5.85 24.7

21 Sacramento River at Tower Bridge (7 days) 41.10 10.90 52
Occurrence and Transport of Diazinon 43

 Because the periods when samples were collected were 

sometimes shorter than the duration of the runoff flows 

defined by the storm hydrographs at the monitoring sites, load 

estimates may be underestimated at some sites. A monitoring 

period of 5 days after rainfall begins, appears to be a sufficient 

time to capture peak diazinon concentrations at the smaller 

streams such as the Wadsworth Canal, but not in some of the 

larger channels. The monitoring period ended at the 

Sacramento River at Alamar, Feather River, and Butte Slough 

before concentrations and loads were observed to peak during 

both storms, despite monitoring at Alamar for six consecutive 

days, a day longer than other upstream sites. Sacramento 

River at Tower Bridge provides a good example of the need 

to continue monitoring until concentrations show a welldocumented declining trend. The total load at that site during 

the first 5 days of monitoring was about 24.7 lb. An additional 

sample collected 2 days later allowed a more complete 

estimate of the storm load at that site. The 7-day storm total of 

52 lb (table 3) represents an increase of 100 percent over the 

5-day total. Because the Sacramento River at Tower Bridge 

site is the site farthest downstream and is integrating runoff 

and diazinon sources throughout the basin, the length of the 

storm hydrograph, the delay of peak concentrations, and the 

period of elevated diazinon concentrations are all expected to 

be greater there than at sites farther upstream on the 

Sacramento and Feather Rivers. Five days of monitoring at 

Sacramento River at Colusa was the minimum length of time 

required to estimate loads at that site in 2001. An additional 

day of sampling at that site would reduce the uncertainty of 

load estimates by including more of the storm hydrograph and 

reducing the time of any extrapolations beyond the last 

sample. In future sampling, consideration should be given to 

collecting samples at Sacramento River at Alamar and Tower 

Bridge for a minimum of 7 days. These time estimates are 

based on conditions encountered in 2001. The suggested time 

periods should be extended if future monitoring occurred 

during much higher flows or longer storm durations.

Relation of Diazinon Loads to Use

In general, diazinon loads were greater in subbasins with 

greater diazinon use. Figure 17 shows the relation between 

use and storm loads during the monitoring periods in the six 

subbasins in which both pesticide use and storm period loads 

were reported. 

0

100 1,000 10,000 100,000

1

10

100

Diazinon load, in pounds

Use vs Load

Sacramento River at

Tower Bridge (0.2%)

Sacramento River at

Colusa (0.2%)

Feather River below

Star Bend (0.06%)

Jack Slough near

Bear River near Doc Adams Road (0.05%)

Berry Road (0.2%) Main Drainage Canal at

Gridley Road (0.9%)

Diazinon use in pounds active ingredient

Figure 17. Diazinon load in relation to use in six subbasins in the Sacramento Valley.

[Numbers in parentheses are percentages of load to upstream use.]
44 Occurrence and Transport of Diazinon, Sacramento River and Selected Tributaries, Calif., during Two Winter Storms, 2001

Estimates of the fraction of applied diazinon transported 

to the Feather and Sacramento Rivers (yield) were made by 

dividing storm loads by the mass of diazinon applied 

upstream in the period before and during the monitored storm 

events. Diazinon applied from December 23 to January 24 

was used in the calculations for the first monitoring period 

(period 2 in table 2), and diazinon applied from January 25 to 

February 9 was used for the second monitoring period 

(period 3 in table 2). 

Although there was some agricultural use of diazinon in 

December (period 1 in table 2), diazinon use during this 

period was not included in the analysis. The field half-life of 

diazinon is reported to be between 3 and 54 days (U.S. 

Department of Agriculture, 2003). The amount of diazinon 

applied in December was relatively small, and sufficient time 

had elapsed between the early applications and the first 

monitored storm at the end of January for significant 

degradation and loss of applied diazinon from the study area. 

Diazinon yield at the Sacramento River (sites 8 and 21) 

during the monitoring periods was approximately 0.02 

percent of the amount applied to upstream agricultural lands. 

Sacramento River at Alamar (site 20) was not included in the 

analysis because the monitoring periods at this site did not 

cover the entire storm hydrographs, so the storm loads would 

have been underestimated.

Storm period loads at Feather River below Star Bend 

(site 18), Jack Slough near Doc Adams Road (site 16), and 

the Main Drainage Canal at Gridley Road (site 10) ranged 

between 0.05 and 0.09 percent of the applied pesticide. The 

amount of applied diazinon transported to Bear River near 

Berry Road (site 19) was 0.02 percent. The estimated amount 

of diazinon transported from agricultural land to the 

Sacramento River and its tributaries was lower in 2001 than 

the previous year. In the 2000 storm runoff study, basin yields 

for the Sacramento River at Tower Bridge (site 21) ranged 

from 0.20 to 0.85 percent, and yields from the Feather River 

ranged from 0.25 to 0.49 percent (Dileanis and others, 2002). 

The quantity of pesticides applied in the Sacramento Valley 

during the 2000 and 2001 dormant spray seasons was just 

over 40,000 lb a.i. in each of the two years. However, there 

were differences in use by subbasin. Diazinon applications 

used to calculate loads upstream of Sacramento River at 

Tower Bridge (site 21) were 27 percent higher in 2000. In the 

Feather River (sites 18 and 19), diazinon applications were 

164 percent higher in 2000 than in 2001. 

Another factor in the decrease in yield observed in 2001 

may have been the amount of rainfall that occurred during the 

monitoring periods. Marysville, located close to the Feather 

River, received 13.7 in. of rain during January and February 

2000. In 2001, 8.7 in. was recorded. The average rainfall 

(1960–90) for January and February at Marysville is 7.2 in. 

(National Oceanic and Atmospheric Administration, 2001). 

The unusually high rainfall in 2000 and the lower diazinon 

use in 2001 is reflected in the lower yields observed in 2001. 

Summary

A portion of the diazinon applications made to orchards 

and urban areas during the winter months in the Sacramento 

Valley of California is transported to streams and agricultural 

drains in storm runoff. In the winter of 2001, diazinon 

concentrations in the Sacramento River and selected 

tributaries ranged from less than 5 ng/L (analytical detection 

level) to 1,380 ng/L, with a median of 55 ng/L during the first 

storm and 26 ng/L during the second storm. The highest 

concentrations were present in small streams draining 

agricultural areas. Concentrations in streams draining the 

Chico urban area were also elevated relative to streams 

draining nonagricultural land.

Load estimates for two storm runoff periods indicate 

that about 30 percent of the diazinon in the lower Sacramento 

River is introduced from the portion of the basin upstream of 

Colusa. Diazinon transported from the Chico urban area does 

not appear to be a large portion of the load observed in the 

Sacramento River at Colusa. 

About 26,000 lb of diazinon were reported applied to 

agricultural land in the Sacramento Valley just before and 

during the monitoring period. About 0.2 percent of the 

applied diazinon appeared to be transported to the lower 

Sacramento River during the period of monitoring. About 

0.06 percent of the applied diazinon was estimated to have 

entered the Feather River from orchard applications in this 

watershed. These yields were lower than those estimated for 

these basins during the previous winter. Lower yields may be 

related in part to lower pesticide use, especially in the Feather 

River watershed.

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Appendixes 47

APPENDIXES
48 Occurrence and Transport of Diazinon, Sacramento River and Selected Tributaries, Calif., during Two Winter Storms, 2001

Appendix 1. Table 1. Diazinon and methidathion concentrations in blank samples analyzed by the California Department of 

Fish and Game's Water Pollution Control Laboratory. 

[ng/L, nanogram per liter; <, less than; DWR, California Department of Water Resources]

Site number Site name Date and time

Diazinon 

concentration

(ng/L)

Methidathion 

concentration

(ng/L)

AMBIENT BLANKS

1 Sacramento River at Hamilton City 02/09/01 1525 <20 <50

7 Stony Creek at Highway 45 02/10/01 1120 <20 <50

9 Butte Creek at Gridley Road 01/24/01 1155 <20 <50

10 Main Drainage Canal at Gridley Road 01/25/01 1830 <20 <50

10 Main Drainage Canal at Gridley Road 02/10/01 0635 <20 <50

11 Butte Slough at Lower Pass Road 01/24/01 1144 <20 <50

11 Butte Slough at Lower Pass Road 02/10/01 1120 <20 <50

13 DWR Pumping Plant 2, North 02/09/01 1310 <20 <50

13 DWR Pumping Plant 2, North 12/14/00 1035 <20 <50

19 Bear River near Berry Road 01/26/01 1120 <20 <50

19 Bear River near Berry Road 02/11/01 1030 <20 <50

FIELD BLANKS

1 Sacramento River at Hamilton City 02/10/01 1210 <20 <50

9 Butte Creek at Gridley Road 02/09/01 1225 <20 <50

9 Butte Creek at Gridley Road 02/11/01 1800 <20 <50

11 Butte Slough at Lower Pass Road 01/25/01 1125 <20 <50

11 Butte Slough at Lower Pass Road 02/11/01 1125 <20 <50

12 Wadsworth Canal at South Butte Road 01/25/01 1140 <20 <50

12 Wadsworth Canal at South Butte Road 02/09/01 1605 <20 <50

14 DWR Pumping Plant 2, South 01/25/01 1255 <20 <50

14 DWR Pumping Plant 2, South 02/10/01 1222 <20 <50

18 Feather River below Star Bend 01/25/01 1150 <20 <50

18 Feather River below Star Bend 02/10/01 1300 <20 <50
Appendix 1. Table 2. 49

Appendix 1. Table 2. Pesticide recovery from spiked samples 

analyzed by the California Department of Fish and Game Water 

Pollution Control Laboratory. 

[μg/L, microgram per liter]

Extraction 

date

Sample

number Pesticide

Spike

level

(μg/L)

Percent

recovery

01/25/01 109 Chlorpyrifos 0.1 97

01/25/01 109 Diazinon 0.2 89

01/25/01 109 Malathion 0.2 96

01/25/01 109 Methidathion 0.1 101

01/25/01 110 Chlorpyrifos 0.1 94

01/25/01 110 Diazinon 0.2 85

01/25/01 110 Malathion 0.2 87

01/25/01 110 Methidathion 0.1 112

02/01/01 112 Chlorpyrifos 0.05 98

02/01/01 112 Diazinon 0.5 87

02/01/01 112 Dimethoate 0.2 110

02/01/01 112 Methidathion 0.2 110

02/04/01 111 Chlorpyrifos 0.05 96

02/04/01 111 Diazinon 0.5 84

02/04/01 111 Dimethoate 0.2 112

02/04/01 111 Methidathion 0.2 105

02/13/01 113 Chlorpyrifos 0.1 91

02/13/01 113 Diazinon 0.5 74

02/13/01 113 Dimethoate 0.2 106

02/13/01 113 Methidathion 0.2 97

02/14/01 117 Chlorpyrifos 0.1 94

02/14/01 117 Diazinon 0.2 84

02/14/01 117 Malathion 0.2 93

02/14/01 117 Methidathion 0.1 108

02/14/01 119 Chlorpyrifos 0.1 97

02/14/01 119 Diazinon 0.5 79

02/14/01 119 Dimethoate 0.2 111

02/14/01 119 Methidathion 0.2 98

02/20/01 115 Chlorpyrifos 0.1 97

02/20/01 115 Diazinon 0.2 86

02/20/01 115 Malathion 0.2 92

02/20/01 115 Methidathion 0.1 102
50 Occurrence and Transport of Diazinon, Sacramento River and Selected Tributaries, Calif., during Two Winter Storms, 2001

Appendix 1. Table 3. Diazinon and methidathion concentrations in replicate samples from sites in the Sacramento River Basin, California, 

analyzed by the California Department of Fish and Game's Water Pollution Control Laboratory. 

[ng/L, nanogram per liter; <, less than; DWR, California Department of Water Resources]

Site No. Site name Date and time Diazinon

(ng/L)

Replicate 

diazinon

(ng/L)

Methidathion

(ng/L)

Replicate

methidathion

(ng/L)

1 Sacramento River at Hamilton City 02/09/01 1525 <20 <20 <50 <50

1 Sacramento River at Hamilton City 02/11/01 1115 <20 <20 <50 <50

1 Sacramento River at Hamilton City 02/12/01 1050 <20 <20 <50 <50

1 Sacramento River at Hamilton City 02/13/01 1010 <20 <20 <50 <50

5 Little Chico Creek 02/10/01 1450 20 <20 <50 <50

7 Stony Creek at Highway 45 02/09/01 1055 21 <20 <50 <50

9 Butte Creek at Gridley Road 01/24/01 2100 58 52 <50 <50

9 Butte Creek at Gridley Road 01/25/01 1025 45 61 <50 <50

9 Butte Creek at Gridley Road 01/25/01 1800 45 49 <50 <50

9 Butte Creek at Gridley Road 01/27/01 0625 40 49 <50 <50

9 Butte Creek at Gridley Road 01/27/01 1800 60 47 <50 <50

9 Butte Creek at Gridley Road 02/10/01 0615 28 <20 <50 <50

9 Butte Creek at Gridley Road 02/12/01 0620 <20 <20 <50 <50

10 Main Drainage Canal at Gridley Road 01/25/01 1045 68 76 <50 <50

10 Main Drainage Canal at Gridley Road 01/26/01 0635 93 98 <50 <50

10 Main Drainage Canal at Gridley Road 01/26/01 1830 63 78 <50 <50

10 Main Drainage Canal at Gridley Road 02/10/01 0635 61 67 <50 <50

10 Main Drainage Canal at Gridley Road 02/11/01 0700 91 87 4,720 4,160

11 Butte Slough at Lower Pass Road 02/14/01 1115 25 <20 <50 <50

12 Wadsworth Canal at South Butte Road 01/26/01 0730 200 223 <50 <50

12 Wadsworth Canal at South Butte Road 01/27/01 0300 256 286 <50 <50

12 Wadsworth Canal at South Butte Road 02/11/01 0825 418 456 <50 <50

13 DWR Pumping Plant 2, North 01/24/01 1230 86 93 <50 <50

14 DWR Pumping Plant 2, South 02/13/01 1254 31 45 3,700 4,500

15 DWR Pumping Plant 1 01/24/01 1140 171 93 <50 <50

15 DWR Pumping Plant 1 02/09/01 1210 111 97 <50 <50

17 Feather River at Yuba City 01/26/01 1240 <20 <20 <50 <50

17 Feather River at Yuba City 02/12/01 1230 <20 <20 <50 <50

19 Bear River near Berry Road 01/25/01 0930 48 52 <50 <50

19 Bear River near Berry Road 02/10/01 1030 42 <20 <50 <50

20 Sacramento River at Alamar 2/11/01 1100 <20 44 <50 <50
Appendix 1. Table 4. 51

Site 

no. Site name Date Time 2,6-Diethyl 

aniline 

Acetochlor

Alachlor

(ng/L)

AlphaBHC

Atrazine

(ng/L)

Benfluralin (ng/L)Butylate

(ng/L)

Blank samples

8 Sacramento River at Colusa 01/28/01 0948 <2 <4 <2 <5 <7 <10 <2

8 Sacramento River at Colusa 02/12/01 1048 <2 <4 <2 <5 <7 <10 <2

18 Feather River below Star Bend 01/25/01 1308 <2 <4 <2 <5 <7 <10 <2

18 Feather River below Star Bend 02/13/01 1138 <2 <4 <2 <5 <7 <10 <2

20 Sacramento River at Alamar 01/28/01 1058 <2 <4 <2 <5 <7 <10 <2

21 Sacramento River at Tower Bridge 02/11/01 1308 <2 <4 <2 <5 <7 <10 <2

Replicate samples

18 Feather River below Star Bend 02/13/01 1131 <2 <4 <2 <5 <7 <10 <2

21 Sacramento River at Tower Bridge 01/29/01 1101 <2 <4 <2 <5 <7 <10 <2

21 Sacramento River at Tower Bridge 02/11/01 1301 <2 <4 <2 <5 <7 <10 <2

8 Sacramento River at Colusa 01/26/01 0941 <2 <4 <2 <5 <7 <10 <2

8 Sacramento River at Colusa 02/14/01 1001 <2 <4 <2 <5 <7 <10 <2

20 Sacramento River at Alamar 01/25/01 1111 <2 <4 <2 <5 <7 <10 <2

20 Sacramento River at Alamar 02/10/01 1051 <2 <4 <2 <5 <7 <10 <2

Site 

no. Site name Date Time Carbaryl(ng/L)

CarbofuranChlorpyrifos

Cyanazine

(ng/L)

DCPA

(ng/L)

Desethyl 

atrazine

Diazinon 

surrogate

Blank samples

8 Sacramento River at Colusa 01/28/01 0948 <41 <20 <5 <18 <3 <6 108

8 Sacramento River at Colusa 02/12/01 1048 <41 <20 <5 <18 <3 <6 89

18 Feather River below Star Bend 01/25/01 1308 <41 <20 <5 <18 <3 <6 97

18 Feather River below Star Bend 02/13/01 1138 <41 <20 <5 <18 <3 <6 91

20 Sacramento River at Alamar 01/28/01 1058 <41 <20 <5 <18 <3 <6 97

21 Sacramento River at Tower Bridge 02/11/01 1308 <41 <20 <5 <18 <3 <6 87

Replicate samples

18 Feather River below Star Bend 02/13/01 1131 <41 <20 <5 <18 <3 <6 108

21 Sacramento River at Tower Bridge 01/29/01 1101 <41 <20 <5 <18 <3 <6 92

21 Sacramento River at Tower Bridge 02/11/01 1301 <41 <20 <5 <18 <3 <6 95

8 Sacramento River at Colusa 01/26/01 0941 <41 <20 E3 <18 <3 <6 126

8 Sacramento River at Colusa 02/14/01 1001 <41 <20 <5 <18 <3 <6 100

20 Sacramento River at Alamar 01/25/01 1111 <41 E6 <5 <18 <3 <6 105

20 Sacramento River at Alamar 02/10/01 1051 <41 <20 <5 <18 <3 <6 84

Appendix 1. Table 4. Pesticide concentrations in blank and replicate samples from sites in the Sacramento River Basin, California, analyzed by the U.S. 

Geological Survey National Water Quality Laboratory. 

[<, less than; E, estimated value; ng/L, nanograms per liter]
52 Occurrence and Transport of Diazinon, Sacramento River and Selected Tributaries, Calif., during Two Winter Storms, 2001

Site 

no. Site name Date Time Diazinon(ng/L)

Dieldrin

(ng/L)

Disulfoton

(ng/L)

EPTC

(ng/L)

Ethalfluralin

Ethoprop

(ng/L)

Fonofos

(ng/L)

Blank samples

8 Sacramento River at Colusa 01/28/01 0948 <5 <5 <21 <2 <9 <5 <3

8 Sacramento River at Colusa 02/12/01 1048 <5 <5 <21 <2 <9 <5 <3

18 Feather River below Star Bend 01/25/01 1308 <5 <5 <21 <2 <9 <5 <3

18 Feather River below Star Bend 02/13/01 1138 <5 <5 <21 <2 <9 <5 <3

20 Sacramento River at Alamar 01/28/01 1058 <5 <5 <21 <2 <9 <5 <3

21 Sacramento River at Tower 

Bridge

02/11/01 1308 <5 <5 <21 <2 <9 <5 <3

Replicate samples

18 Feather River below Star Bend 02/13/01 1131 16 <5 <21 <2 <9 <5 <3

21 Sacramento River at Tower 

Bridge

01/29/01 1101 60 <5 <21 <2 <9 <5 <3

21 Sacramento River at Tower 

Bridge

02/11/01 1301 12 <5 <21 <2 <9 <5 <3

8 Sacramento River at Colusa 01/26/01 0941 39 <5 <21 <2 <9 <5 <3

8 Sacramento River at Colusa 02/14/01 1001 10 <5 <21 <2 <9 <5 <3

20 Sacramento River at Alamar 01/25/01 1111 24 <5 <21 <2 <9 <5 <3

20 Sacramento River at Alamar 02/10/01 1051 11 <5 <21 <2 <9 <5 <3

Site 

no. Site name Date Time Alpha-D6 

HCH

Lindane

(ng/L)

Linuron

(ng/L)

Malathion

(ng/L)

Methyl 

azinphos

Methyl 

parathion

Metolachlor

Blank samples

8 Sacramento River at Colusa 01/28/01 0948 107 <4 <35 <27 <50 <6 <13

8 Sacramento River at Colusa 02/12/01 1048 73 <4 <35 <27 <50 <6 <13

18 Feather River below Star Bend 01/25/01 1308 101 <4 <35 <27 <50 <6 <13

18 Feather River below Star Bend 02/13/01 1138 97 <4 <35 <27 <50 <6 <13

20 Sacramento River at Alamar 01/28/01 1058 102 <4 <35 <27 <50 <6 <13

21 Sacramento River at Tower 

Bridge

02/11/01 1308 77 <4 <35 <27 <50 <6 <13

Replicate samples

18 Feather River below Star Bend 02/13/01 1131 117 <4 <35 <27 <50 <6 <13

21 Sacramento River at Tower 

Bridge

01/29/01 1101 84 <4 <35 <27 <50 <6 <13

21 Sacramento River at Tower 

Bridge

02/11/01 1301 79 <4 <35 <27 <50 <6 <13

8 Sacramento River at Colusa 01/26/01 0941 120 <4 <35 <27 <50 <6 E8

8 Sacramento River at Colusa 02/14/01 1001 117 <4 <35 <27 <50 <6 <13

20 Sacramento River at Alamar 01/25/01 1111 107 <4 <35 <27 <50 <6 E1

20 Sacramento River at Alamar 02/10/01 1051 69 <4 <35 <27 <50 <6 <13

Appendix 1. Table 4. Pesticide concentrations in blank and replicate samples from sites in the Sacramento River Basin, California, analyzed by the U.S. 

Geological Survey National Water Quality Laboratory—Continued. 
Appendix 1. Table 4. 53

Site 

no. Site name Date Time Metribuzin

(ng/L)

Molinate

(ng/L)

Napropamide

p,p'-DDE

(ng/L)

Parathion

(ng/L)

Pebulate

(ng/L)

Pendimethalin

Blank samples

8 Sacramento River at Colusa 01/28/01 0948 <6 <2 <7 <3 <7 <2 <10

8 Sacramento River at Colusa 02/12/01 1048 <6 <2 <7 <3 <7 <2 <10

18 Feather River below Star Bend 01/25/01 1308 <6 <2 <7 <3 <7 <2 <10

18 Feather River below Star Bend 02/13/01 1138 <6 <2 <7 <3 <7 <2 <10

20 Sacramento River at Alamar 01/28/01 1058 <6 <2 <7 <3 <7 <2 <10

21 Sacramento River at Tower 

Bridge

02/11/01 1308 <6 <2 <7 <3 <7 <2 <10

Replicate samples

18 Feather River below Star Bend 02/13/01 1131 <6 10 <7 <3 <7 <2 <10

21 Sacramento River at Tower 

Bridge

01/29/01 1101 <6 9 <7 <3 <7 <2 <10

21 Sacramento River at Tower 

Bridge

02/11/01 1301 <6 25 <7 <3 <7 <2 <10

8 Sacramento River at Colusa 01/26/01 0941 <6 <2 <7 <3 <7 <2 <10

8 Sacramento River at Colusa 02/14/01 1001 <6 <2 <7 <3 <7 <2 <10

20 Sacramento River at Alamar 01/25/01 1111 <6 22 <7 <3 <7 <2 <10

20 Sacramento River at Alamar 02/10/01 1051 <6 19 <7 <3 <7 <2 <10

Site 

no. Site name Date Time Permethrin(ng/L)

Phorate

(ng/L)

Prometon

(ng/L)

Pronamide

(ng/L)

Propachlor

(ng/L)

Propanil

(ng/L)

Propargite

(ng/L)

Blank samples

8 Sacramento River at Colusa 01/28/01 0948 <6 <11 <15 <4 <10 <11 <23

8 Sacramento River at Colusa 02/12/01 1048 <6 <11 <15 <4 <10 <11 <23

18 Feather River below Star Bend 01/25/01 1308 <6 <11 <15 <4 <10 <11 <23

18 Feather River below Star Bend 02/13/01 1138 <6 <11 <15 <4 <10 <11 <23

20 Sacramento River at Alamar 01/28/01 1058 <6 <11 <15 <4 <10 E1 <23

21 Sacramento River at Tower Bridge 02/11/01 1308 <6 <11 <15 <4 <10 <11 <23

Replicate samples

18 Feather River below Star Bend 02/13/01 1131 <6 <11 <15 <4 <10 <11 <23

21 Sacramento River at Tower Bridge 01/29/01 1101 <6 <11 <15 17 <10 <11 <23

21 Sacramento River at Tower Bridge 02/11/01 1301 <6 <11 <15 <4 <10 <11 <23

8 Sacramento River at Colusa 01/26/01 0941 <6 <11 <15 <4 <10 <11 <23

8 Sacramento River at Colusa 02/14/01 1001 <6 <11 <15 <4 <10 <11 <23

20 Sacramento River at Alamar 01/25/01 1111 <6 <11 <15 E3 <10 <11 <23

20 Sacramento River at Alamar 02/10/01 1051 <6 <11 <15 6 <10 <11 <23

Appendix 1. Table 4. Pesticide concentrations in blank and replicate samples from sites in the Sacramento River Basin, California, analyzed by the U.S. 

Geological Survey National Water Quality Laboratory—Continued. 
54 Occurrence and Transport of Diazinon, Sacramento River and Selected Tributaries, Calif., during Two Winter Storms, 2001

Site 

no. Site name Date Time Simazine(ng/L)

Tebuthiuron

(ng/L)

Terbacil

(ng/L)

Terbufos

(ng/L)

Thiobencarb

(ng/L)

Triallate

(ng/L)

Trifluralin

(ng/L)

Blank samples

8 Sacramento River at Colusa 01/28/01 0948 <11 <16 <34 <17 <5 <2 <9

8 Sacramento River at Colusa 02/12/01 1048 <11 <16 <34 <17 <5 <2 <9

18 Feather River below Star Bend 01/25/01 1308 <11 <16 <34 <17 <5 <2 <9

18 Feather River below Star Bend 02/13/01 1138 <11 <16 <34 <17 <5 <2 <9

20 Sacramento River at Alamar 01/28/01 1058 <11 <16 <34 <17 <5 <2 <9

21 Sacramento River at Tower Bridge 02/11/01 1308 <11 <16 <34 <17 <5 <2 <9

Replicate samples

18 Feather River below Star Bend 02/13/01 1131 18 <16 <34 <17 E4 <2 <9

21 Sacramento River at Tower Bridge 01/29/01 1101 69 <16 <34 <17 <5 <2 <9

21 Sacramento River at Tower Bridge 02/11/01 1301 <11 <16 <34 <17 <10 <2 <9

8 Sacramento River at Colusa 01/26/01 0941 24 <16 <34 <17 <5 <2 <9

8 Sacramento River at Colusa 02/14/01 1001 21 <16 <34 <17 <5 <2 <9

20 Sacramento River at Alamar 01/25/01 1111 E11 <16 <34 <17 10 <2 <9

20 Sacramento River at Alamar 02/10/01 1051 <11 <16 <34 <17 6 <2 <9

Appendix 1. Table 4. Pesticide concentrations in blank and replicate samples from sites in the Sacramento River Basin, California, analyzed by the U.S. 

Geological Survey National Water Quality Laboratory—Continued. 
Appendix 2. Table 1. 55

Appendix 1. Table 5. Pesticide recovery from spiked samples analyzed by the U.S. Geological Survey National Water Quality Laboratory. 

[Spike for all analytes was 0.1 μg (microgram)]

Pesticides

Sacramento River 

at Colusa (site 8) 

recovery, in 

percent (2/10/01 

9:30)

Sacramento River 

at Alamar (site 20) 

recovery, in 

percent (1/26/01 

8:40)

Pesticides

Sacramento River 

at Colusa (site 8) 

recovery, in 

percent (2/10/01 

9:30)

Sacramento River 

at Alamar (site 20) 

recovery, in 

percent (1/26/01 

8:40)

2,6-Diethyl aniline 184 87 Methyl Parathion 67 115

Acetochlor 111 131 Metolachlor 120 131

Alachlor 109 123 Metribuzin 79 113

Alpha-BHC 75 104 Molinate 94 103

Atrazine 86 116 Napropamide 80 132

Benfluralin 55 89 p,p'-DDE 39 48

Butylate 97 98 Parathion 65 136

Carbaryl 276 595 Pebulate 99 100

Carbofuran 281 454 Pendimethalin 52 118

Chlorpyrifos 63 93 Permethrin 32 36

Cyanazine 87 216 Phorate 64 73

DCPA 69 114 Prometon 35 48

Desethyl Atrazine 53 81 Pronamide 81 115

Diazinon 97 111 Propachlor 94 117

Dieldrin 95 103 Propanil 73 126

Disulfoton 46 50 Propargite 86 112

EPTC 158 95 Simazine 85 121

Ethalfluralin 66 110 Tebuthiuron 87 139

Ethoprop 70 104 Terbacil 147 161

Fonofos 97 102 Terbufos 63 92

Lindane 81 109 Thiobencarb 93 117

Linuron 105 158 Triallate 97 104

Malathion 102 156 Trifluralin 52 102

Methyl Azinphos 43 264
56 Occurrence and Transport of Diazinon, Sacramento River and Selected Tributaries, Calif., during Two Winter Storms, 2001

Appendix 2. Table 1. Diazinon and methidathion concentrations in environmental samples from the Sacramento 

River Basin, California, analyzed by the California Dept. of Fish and Game Water Pollution Control Laboratory—

Continued. 

Site no. Site name Date Time Diazinon

(ng/L)

Methidathion 

(ng/L)

1 Sacramento River at Hamilton City 02/09/01 1525 <20 <50

1 Sacramento River at Hamilton City 02/10/01 1210 <20 <50

1 Sacramento River at Hamilton City 02/11/01 1115 <20 <50

1 Sacramento River at Hamilton City 02/12/01 1050 <20 <50

1 Sacramento River at Hamilton City 02/13/01 1010 <20 <50

1 Sacramento River at Hamilton City 02/14/01 1110 <20 <50

2 Mud Creek at Chico 02/09/01 1600 48 <50

2 Mud Creek at Chico 02/10/01 1310 20 <50

3 Lindo Channel at Chico 02/09/01 1655 129 <50

3 Lindo Channel at Chico 02/10/01 1340 185 <50

4 Big Chico Creek at Chico 02/09/01 1210 24 <50

4 Big Chico Creek at Chico 02/09/01 1910 <20 <50

4 Big Chico Creek at Chico 02/10/01 0850 <20 <50

4 Big Chico Creek at Chico 02/10/01 1525 <20 <50

4 Big Chico Creek at Chico 02/11/01 0855 20 <50

4 Big Chico Creek at Chico 02/11/01 1510 <20 <50

4 Big Chico Creek at Chico 02/12/01 1445 <20 <50

4 Big Chico Creek at Chico 02/13/01 0825 <20 <50

4 Big Chico Creek at Chico 02/12/01 0835 <20 <50

5 Little Chico Creek 02/09/01 1335 133 <50

5 Little Chico Creek 02/10/01 1450 20 <50

6 Big Chico Creek at River Rd. 02/09/01 0920 <20 <50

6 Big Chico Creek at River Rd. 02/09/01 1755 62 <50

6 Big Chico Creek at River Rd. 02/10/01 1020 <20 <50

6 Big Chico Creek at River Rd. 02/10/01 1600 22 <50

6 Big Chico Creek at River Rd. 02/11/01 0945 <20 <50

6 Big Chico Creek at River Rd. 02/11/01 1725 <20 <50

6 Big Chico Creek at River Rd. 02/12/01 0920 <20 <50

6 Big Chico Creek at River Rd. 02/12/01 1515 <20 <50

6 Big Chico Creek at River Rd. 02/13/01 0900 <20 <50

7 Stony Creek at Highway 45 02/09/01 1055 21 <50

7 Stony Creek at Highway 45 02/10/01 1120 <20 <50

8 Sacramento River at Colusa 01/24/01 1020 19 <50

8 Sacramento River at Colusa 01/25/01 0944 <20 <50

Appendix 2. Table 1. Diazinon and methidathion concentrations in environmental samples from the Sacramento 

River Basin, California, analyzed by the California Dept. of Fish and Game Water Pollution Control Laboratory. 

[(1) Sample collected as part of California Dept. of Pesticide Regulation's Dormant Spray Program, no sample time 

given; <, less than; ng/L, nanogram per liter. All data in table available from the California Department of Pesticide 

Regulation]
Appendix 2. Table 1. 57

Site no. Site name Date Time Diazinon

(ng/L)

Methidathion 

(ng/L)

8 Sacramento River at Colusa 01/26/01 0940 34 <50

8 Sacramento River at Colusa 01/27/01 1040 32 <50

8 Sacramento River at Colusa 01/28/01 1020 25 <50

8 Sacramento River at Colusa 02/10/01 1020 <20 <50

8 Sacramento River at Colusa 02/11/01 1045 <20 <50

8 Sacramento River at Colusa 02/12/01 1045 20 <50

8 Sacramento River at Colusa 02/13/01 1030 <20 <50

8 Sacramento River at Colusa 02/14/01 1000 <20 <50

9 Butte Creek at Gridley Road 01/24/01 1155 47 <50

9 Butte Creek at Gridley Road 01/24/01 2100 58 <50

9 Butte Creek at Gridley Road 01/25/01 1025 45 <50

9 Butte Creek at Gridley Road 01/25/01 1445 49 <50

9 Butte Creek at Gridley Road 01/25/01 1800 45 <50

9 Butte Creek at Gridley Road 01/25/01 2200 41 <50

9 Butte Creek at Gridley Road 01/26/01 0200 46 <50

9 Butte Creek at Gridley Road 01/26/01 0620 43 <50

9 Butte Creek at Gridley Road 01/26/01 1010 39 <50

9 Butte Creek at Gridley Road 01/26/01 1410 44 <50

9 Butte Creek at Gridley Road 01/26/01 1800 48 <50

9 Butte Creek at Gridley Road 01/26/01 2200 43 <50

9 Butte Creek at Gridley Road 01/27/01 0000 55 <50

9 Butte Creek at Gridley Road 01/27/01 0200 47 <50

9 Butte Creek at Gridley Road 01/27/01 0625 40 <50

9 Butte Creek at Gridley Road 01/27/01 1205 59 <50

9 Butte Creek at Gridley Road 01/27/01 1800 60 <50

9 Butte Creek at Gridley Road 01/28/01 0745 55 <50

9 Butte Creek at Gridley Road 02/09/01 1225 32 <50

9 Butte Creek at Gridley Road 02/09/01 1815 28 <50

9 Butte Creek at Gridley Road 02/09/01 2217 28 <50

9 Butte Creek at Gridley Road 02/10/01 0220 26 <50

9 Butte Creek at Gridley Road 02/10/01 0615 28 <50

9 Butte Creek at Gridley Road 02/10/01 1030 24 <50

9 Butte Creek at Gridley Road 02/10/01 1525 23 <50

9 Butte Creek at Gridley Road 02/10/01 1855 22 <50

9 Butte Creek at Gridley Road 02/10/01 2205 22 <50

9 Butte Creek at Gridley Road 02/11/01 0210 25 <50

Appendix 2. Table 1. Diazinon and methidathion concentrations in environmental samples from the Sacramento 

River Basin, California, analyzed by the California Dept. of Fish and Game Water Pollution Control Laboratory—

Continued. 
58 Occurrence and Transport of Diazinon, Sacramento River and Selected Tributaries, Calif., during Two Winter Storms, 2001

Site no. Site name Date Time Diazinon

(ng/L)

Methidathion 

(ng/L)

9 Butte Creek at Gridley Road 02/11/01 0610 20 <50

9 Butte Creek at Gridley Road 02/11/01 1015 23 <50

9 Butte Creek at Gridley Road 02/11/01 1405 24 <50

9 Butte Creek at Gridley Road 02/11/01 2205 <20 <50

9 Butte Creek at Gridley Road 02/12/01 0005 <20 <50

9 Butte Creek at Gridley Road 02/12/01 0210 <20 <50

9 Butte Creek at Gridley Road 02/12/01 0620 <20 <50

9 Butte Creek at Gridley Road 02/12/01 1130 20 <50

9 Butte Creek at Gridley Road 02/12/01 1430 20 <50

9 Butte Creek at Gridley Road 02/12/01 1815 <20 <50

9 Butte Creek at Gridley Road 02/13/01 1030 21 <50

9 Butte Creek at Gridley Road 2/11/01 1800 20 <50

10 Main Canal at Gridley Road 01/24/01 1220 92 <50

10 Main Drainage Canal at Gridley Road 01/24/01 2135 69 <50

10 Main Drainage Canal at Gridley Road 01/25/01 1045 68 <50

10 Main Drainage Canal at Gridley Road 01/25/01 1510 63 <50

10 Main Drainage Canal at Gridley Road 01/25/01 1830 67 <50

10 Main Drainage Canal at Gridley Road 01/25/01 2230 101 <50

10 Main Drainage Canal at Gridley Road 01/26/01 0230 96 <50

10 Main Drainage Canal at Gridley Road 01/26/01 0635 93 <50

10 Main Drainage Canal at Gridley Road 01/26/01 1025 79 <50

10 Main Drainage Canal at Gridley Road 01/26/01 1440 68 <50

10 Main Drainage Canal at Gridley Road 01/26/01 1830 63 <50

10 Main Drainage Canal at Gridley Road 01/26/01 2230 65 <50

10 Main Drainage Canal at Gridley Road 01/27/01 0030 53 <50

10 Main Drainage Canal at Gridley Road 01/27/01 0230 55 <50

10 Main Drainage Canal at Gridley Road 01/27/01 0650 61 <50

10 Main Drainage Canal at Gridley Road 01/27/01 1240 53 <50

10 Main Drainage Canal at Gridley Road 01/27/01 1830 57 <50

10 Main Drainage Canal at Gridley Road 01/28/01 0810 49 <50

10 Main Drainage Canal at Gridley Road 02/09/01 1250 20 <50

10 Main Drainage Canal at Gridley Road 02/09/01 1836 23 <50

10 Main Drainage Canal at Gridley Road 02/09/01 2240 101 <50

10 Main Drainage Canal at Gridley Road 02/10/01 0238 83 <50

10 Main Drainage Canal at Gridley Road 02/10/01 0635 61 <50

10 Main Drainage Canal at Gridley Road 02/10/01 1055 51 <50

Appendix 2. Table 1. Diazinon and methidathion concentrations in environmental samples from the Sacramento 

River Basin, California, analyzed by the California Dept. of Fish and Game Water Pollution Control Laboratory—

Continued. 
Appendix 2. Table 1. 59

Site no. Site name Date Time Diazinon

(ng/L)

Methidathion 

(ng/L)

10 Main Drainage Canal at Gridley Road 02/10/01 1540 47 <50

10 Main Drainage Canal at Gridley Road 02/10/01 1910 44 <50

10 Main Drainage Canal at Gridley Road 02/10/01 2220 54 <50

10 Main Drainage Canal at Gridley Road 02/11/01 0220 92 <50

10 Main Drainage Canal at Gridley Road 02/11/01 0700 91 4720

10 Main Drainage Canal at Gridley Road 02/11/01 1030 95 3810

10 Main Drainage Canal at Gridley Road 02/11/01 1430 175 2580

10 Main Drainage Canal at Gridley Road 02/11/01 1815 134 2180

10 Main Drainage Canal at Gridley Road 02/11/01 2220 101 2220

10 Main Drainage Canal at Gridley Road 02/12/01 0015 83 920

10 Main Drainage Canal at Gridley Road 02/12/01 0220 97 2000

10 Main Drainage Canal at Gridley Road 02/12/01 0640 89 1030

10 Main Drainage Canal at Gridley Road 02/12/01 1200 101 698

10 Main Drainage Canal at Gridley Road 02/12/01 1440 104 829

10 Main Drainage Canal at Gridley Road 02/12/01 1830 75 1100

10 Main Drainage Canal at Gridley Road 02/13/01 1045 47 465

11 Butte Slough at Lower Pass Road 01/24/01 1144 <20 <50

11 Butte Slough at Lower Pass Road 01/25/01 1125 28 <50

11 Butte Slough at Lower Pass Road 01/26/01 1120 32 <50

11 Butte Slough at Lower Pass Road 01/27/01 1120 40 <50

11 Butte Slough at Lower Pass Road 01/28/01 1115 53 <50

11 Butte Slough at Lower Pass Road 02/09/01 1200 30 <50

11 Butte Slough at Lower Pass Road 02/10/01 1120 36 <50

11 Butte Slough at Lower Pass Road 02/11/01 1135 38 <50

11 Butte Slough at Lower Pass Road 02/12/01 1115 27 <50

11 Butte Slough at Lower Pass Road 02/13/01 1115 20 <50

11 Butte Slough at Lower Pass Road 02/14/01 1115 25 <50

12 Wadsworth canal at South Butte Road 01/24/01 2240 171 <50

12 Wadsworth canal at South Butte Road 01/25/01 1140 101 <50

12 Wadsworth canal at South Butte Road 01/25/01 1900 140 <50

12 Wadsworth canal at South Butte Road 01/25/01 2300 277 <50

12 Wadsworth canal at South Butte Road 01/26/01 0300 210 <50

12 Wadsworth canal at South Butte Road 01/26/01 0730 200 <50

12 Wadsworth canal at South Butte Road 01/26/01 1245 352 <50

12 Wadsworth canal at South Butte Road 01/26/01 1650 345 <50

12 Wadsworth canal at South Butte Road 01/26/01 1900 433 <50

Appendix 2. Table 1. Diazinon and methidathion concentrations in environmental samples from the Sacramento 

River Basin, California, analyzed by the California Dept. of Fish and Game Water Pollution Control Laboratory—

Continued. 
60 Occurrence and Transport of Diazinon, Sacramento River and Selected Tributaries, Calif., during Two Winter Storms, 2001

Site no. Site name Date Time Diazinon

(ng/L)

Methidathion 

(ng/L)

12 Wadsworth canal at South Butte Road 01/26/01 2300 355 <50

12 Wadsworth canal at South Butte Road 01/27/01 0300 256 <50

12 Wadsworth canal at South Butte Road 01/27/01 0740 232 <50

12 Wadsworth canal at South Butte Road 01/27/01 1505 221 <50

12 Wadsworth canal at South Butte Road 01/27/01 1900 146 <50

12 Wadsworth canal at South Butte Road 01/28/01 0100 161 <50

12 Wadsworth canal at South Butte Road 01/28/01 1025 109 <50

12 Wadsworth canal at South Butte Road 02/09/01 1605 38 <50

12 Wadsworth canal at South Butte Road 02/09/01 1920 61 <50

12 Wadsworth canal at South Butte Road 02/09/01 2320 358 <50

12 Wadsworth canal at South Butte Road 02/10/01 0320 207 <50

12 Wadsworth canal at South Butte Road 02/10/01 0735 1380 <50

12 Wadsworth canal at South Butte Road 02/10/01 1410 513 <50

12 Wadsworth canal at South Butte Road 02/10/01 2000 872 <50

12 Wadsworth canal at South Butte Road 02/10/01 2300 630 <50

12 Wadsworth canal at South Butte Road 02/11/01 0300 453 <50

12 Wadsworth canal at South Butte Road 02/11/01 0825 418 <50

12 Wadsworth canal at South Butte Road 02/11/01 1300 770 <50

12 Wadsworth canal at South Butte Road 02/11/01 1900 829 50

12 Wadsworth canal at South Butte Road 02/11/01 2300 323 <50

12 Wadsworth canal at South Butte Road 02/12/01 0055 368 <50

12 Wadsworth canal at South Butte Road 02/12/01 0305 381 <50

12 Wadsworth canal at South Butte Road 02/12/01 0725 293 <50

12 Wadsworth canal at South Butte Road 02/12/01 1520 322 <50

12 Wadsworth canal at South Butte Road 02/12/01 1915 419 <50

12 Wadsworth canal at South Butte Road 02/13/01 0930 292 <50

13 DWR Pumping Plant 2, North 01/24/01 1230 86 <50

13 DWR Pumping Plant 2, North 01/25/01 1240 80 <50

13 DWR Pumping Plant 2, North 01/26/01 1300 70 <50

13 DWR Pumping Plant 2, North 01/27/01 1300 63 <50

13 DWR Pumping Plant 2, North 01/28/01 1230 78 <50

13 DWR Pumping Plant 2, North 02/09/01 1310 24 <50

13 DWR Pumping Plant 2, North 02/10/01 1239 25 <50

13 DWR Pumping Plant 2, North 02/11/01 1217 38 <50

13 DWR Pumping Plant 2, North 02/12/01 1240 61 <50

13 DWR Pumping Plant 2, North 02/13/01 1245 38 <50

Appendix 2. Table 1. Diazinon and methidathion concentrations in environmental samples from the Sacramento 

River Basin, California, analyzed by the California Dept. of Fish and Game Water Pollution Control Laboratory—

Continued. 
Appendix 2. Table 1. 61

Site no. Site name Date Time Diazinon

(ng/L)

Methidathion 

(ng/L)

14 DWR Pumping Plant 1 01/24/01 1140 171 <50

14 DWR Pumping Plant 2, South 01/24/01 1245 32 <50

14 DWR Pumping Plant 1 01/25/01 1210 275 <50

14 DWR Pumping Plant 2, South 01/25/01 1255 55 179

14 DWR Pumping Plant 2, South 01/26/01 1315 50 80

14 DWR Pumping Plant 1 01/26/01 1413 355 <50

14 DWR Pumping Plant 1 01/27/01 1210 156 69

14 DWR Pumping Plant 2, South 01/27/01 1245 135 956

14 DWR Pumping Plant 1 01/28/01 1140 191 <50

14 DWR Pumping Plant 2, South 01/28/01 1240 255 156

14 DWR Pumping Plant 1 02/09/01 1210 111 <50

14 DWR Pumping Plant 2, South 02/09/01 1250 <20 <50

14 DWR Pumping Plant 1 02/10/01 1055 125 <50

14 DWR Pumping Plant 2, South 02/10/01 1222 58 <50

14 DWR Pumping Plant 1 02/11/01 1130 141 <50

14 DWR Pumping Plant 2, South 02/11/01 1203 143 <50

14 DWR Pumping Plant 2, South 02/12/01 1250 31 <50

14 DWR Pumping Plant 2, South 02/13/01 1254 31 370

14 DWR Pumping Plant 1 2/12/01 1200 107 <50

14 DWR Pumping Plant 1 2/13/01 1209 75 <50

16 Jack Slough near Doc Adams Road 01/24/01 1400 103 <50

16 Jack Slough near Doc Adams Road 01/25/01 1400 95 <50

16 Jack Slough near Doc Adams Road 01/26/01 1320 69 <50

16 Jack Slough near Doc Adams Road 01/27/01 1315 86 <50

16 Jack Slough near Doc Adams Road 01/28/01 1255 105 <50

16 Jack Slough near Doc Adams Road 02/09/01 1315 96 <50

16 Jack Slough near Doc Adams Road 02/10/01 1245 86 <50

16 Jack Slough near Doc Adams Road 02/11/01 1245 102 <50

16 Jack Slough near Doc Adams Road 02/12/01 1300 66 <50

16 Jack Slough near Doc Adams Road 02/13/01 1230 68 <50

16 Jack Slough near Doc Adams Road 02/14/01 1220 53 <50

17 Feather River near Yuba City 01/24/01 1342 18 <50

17 Feather River near Yuba City 01/25/01 1325 <20 <50

17 Feather River near Yuba City 01/26/01 1240 <20 <50

17 Feather River near Yuba City 01/27/01 1240 <20 <50

17 Feather River near Yuba City 01/28/01 1230 <20 <50

Appendix 2. Table 1. Diazinon and methidathion concentrations in environmental samples from the Sacramento 

River Basin, California, analyzed by the California Dept. of Fish and Game Water Pollution Control Laboratory—

Continued. 
62 Occurrence and Transport of Diazinon, Sacramento River and Selected Tributaries, Calif., during Two Winter Storms, 2001

Site no. Site name Date Time Diazinon

(ng/L)

Methidathion 

(ng/L)

17 Feather River near Yuba City 02/10/01 1210 <20 <50

17 Feather River near Yuba City 02/11/01 1210 <20 <50

17 Feather River near Yuba City 02/12/01 1230 <20 <50

17 Feather River near Yuba City 02/13/01 1200 <20 <50

17 Feather River near Yuba City 02/14/01 1150 20 <50

18 Feather River at Star Bend 01/24/01 1520 24 <50

18 Feather River at Star Bend 01/25/01 1300 <20 <50

18 Feather River at Star Bend 01/26/01 1400 22 <50

18 Feather River at Star Bend 01/27/01 1330 <20 <50

18 Feather River at Star Bend 01/28/01 1230 <20 <50

18 Feather River at Star Bend 02/10/01 1300 <20 <50

18 Feather River at Star Bend 02/11/01 1300 <20 <50

18 Feather River at Star Bend 2/12/01 1300 <20 <50

18 Feather River at Star Bend 2/13/01 1130 <20 <50

18 Feather River at Star Bend 2/14/01 1040 <20 <50

19 Bear River near Berry Road 01/24/01 1720 55 <50

19 Bear River near Berry Road 01/25/01 0930 48 <50

19 Bear River near Berry Road 01/26/01 1120 54 <50

19 Bear River near Berry Road 01/27/01 1030 55 <50

19 Bear River near Berry Road 01/28/01 1000 40 <50

19 Bear River near Berry Road 02/09/01 1050 50 <50

19 Bear River near Berry Road 02/10/01 1030 42 <50

19 Bear River near Berry Road 02/11/01 1030 26 <50

19 Bear River near Berry Road 02/12/01 1100 43 <50

19 Bear River near Berry Road 02/13/01 1000 33 <50

20 Sacramento River at Alamar 01/24/01 (1) <20 <50

20 Sacramento River at Alamar 01/25/01 1115 28 <50

20 Sacramento River at Alamar 01/26/01 (1) <20 <50

20 Sacramento River at Alamar 01/27/01 1115 41 <50

20 Sacramento River at Alamar 01/28/01 1053 69 <50

20 Sacramento River at Alamar 01/29/01 (1) 48 <50

20 Sacramento River at Alamar 02/09/01 (1) <20 <50

20 Sacramento River at Alamar 02/10/01 1050 <20 <50

20 Sacramento River at Alamar 2/11/01 1100 <20 <50

20 Sacramento River at Alamar 2/12/01 1115 20 <50

20 Sacramento River at Alamar 2/13/01 1115 <20 <50

Appendix 2. Table 1. Diazinon and methidathion concentrations in environmental samples from the Sacramento 

River Basin, California, analyzed by the California Dept. of Fish and Game Water Pollution Control Laboratory—

Continued. 
Appendix 2. Table 2. 63

Site 

no. Site name Date Time

2,6-Diethyl 

aniline

(ng/L)

Acetochlor

(ng/L)

Alachlor

(ng/L)

Alpha-BHC

(ng/L)

Atrazine

(ng/L)

Benfluralin

(ng/L)

Butylate

(ng/L)

8 Sacramento River at Colusa 1/24/01 0940 <2 <4 <2 <5 <7 <10 <2

8 Sacramento River at Colusa 1/25/01 1020 <2 <4 <2 <5 <7 <10 <2

8 Sacramento River at Colusa 1/26/01 0940 <2 <4 <2 <5 <7 <10 <2

8 Sacramento River at Colusa 1/27/01 1040 <2 <4 <2 <5 E3 <10 <2

8 Sacramento River at Colusa 1/28/01 0940 <2 <4 <2 <5 <7 <10 <2

8 Sacramento River at Colusa 2/10/01 0930 <2 <4 <2 <5 <7 <10 <2

8 Sacramento River at Colusa 2/11/01 1040 <2 <4 <2 <5 <7 <10 <2

8 Sacramento River at Colusa 2/12/01 1040 <2 <4 <2 <5 <7 <10 <2

8 Sacramento River at Colusa 2/13/01 0930 <2 <4 <2 <5 <7 <10 <2

8 Sacramento River at Colusa 2/14/01 1000 <2 <4 <2 <5 <7 <10 <2

18 Feather River Below Star Bend 1/24/01 1520 <2 <4 <2 <5 <7 <10 <2

18 Feather River Below Star Bend 1/25/01 1300 <2 <4 <2 <5 <7 <10 <2

18 Feather River Below Star Bend 1/26/01 1400 <2 <4 <2 <5 <7 <10 <2

18 Feather River Below Star Bend 1/27/01 1330 <2 <4 <2 <5 E3 <10 <2

18 Feather River Below Star Bend 1/28/01 1230 <2 <4 <2 <5 E2 <10 <2

18 Feather River Below Star Bend 2/10/01 1300 <2 <4 <2 <5 <7 <10 <2

18 Feather River Below Star Bend 2/11/01 1330 <2 <4 <2 <5 <7 <10 <2

18 Feather River Below Star Bend 2/12/01 1300 <2 <4 <2 <5 <7 <10 <2

18 Feather River Below Star Bend 2/13/01 1130 <2 <4 <2 <5 <7 <10 <2

18 Feather River Below Star Bend 2/14/01 1040 <2 <4 <2 <5 <7 <10 <2

20 Sacramento River at Alamar 1/24/01 1010 <2 <4 <2 <5 <7 <10 <2

20 Sacramento River at Alamar 1/25/01 1110 <2 <4 <2 <5 <7 <10 <2

20 Sacramento River at Alamar 1/26/01 0840 <2 <4 <2 <5 E1 <10 <2

20 Sacramento River at Alamar 1/27/01 1110 <2 <4 <2 <5 <7 <10 <2

20 Sacramento River at Alamar 1/28/01 1050 <2 <4 <2 <5 <7 <10 <2

20 Sacramento River at Alamar 2/9/01 0930 <2 <4 <2 <5 <7 <10 <2

20 Sacramento River at Alamar 2/10/01 1050 <2 <4 <2 <5 <7 <10 <2

20 Sacramento River at Alamar 2/11/01 1030 <2 <4 <2 <5 <7 <10 <2

20 Sacramento River at Alamar 2/12/01 1040 <2 <4 <2 <5 <7 <10 <2

20 Sacramento River at Alamar 2/13/01 1110 <2 <4 <2 <5 <7 <10 <2

20 Sacramento River at Alamar 2/14/01 1010 <2 <4 <2 <5 <7 <10 <2

21 Sacramento River at Tower Bridge 1/25/01 0900 <2 <4 <2 <5 <7 <10 <2

21 Sacramento River at Tower Bridge 1/26/01 1100 <2 <4 <2 <5 <7 <10 <2

21 Sacramento River at Tower Bridge 1/27/01 1100 <2 <4 <2 <5 <7 <10 <2

21 Sacramento River at Tower Bridge 1/28/01 0800 <2 <4 <2 <5 <7 <10 <2

21 Sacramento River at Tower Bridge 1/29/01 1100 <2 <4 <2 <5 <7 <10 <2

21 Sacramento River at Tower Bridge 1/31/01 1130 <2 <4 <2 <5 <7 <10 <2

21 Sacramento River at Tower Bridge 2/10/01 1600 <2 <4 <2 <5 <7 <10 <2

21 Sacramento River at Tower Bridge 2/11/01 1300 <2 <4 <2 <5 <7 <10 <2

21 Sacramento River at Tower Bridge 2/12/01 1300 <2 <4 <2 <5 <7 <10 <2

21 Sacramento River at Tower Bridge 2/13/01 1330 <2 <4 <2 <5 <7 <10 <2

21 Sacramento River at Tower Bridge 2/14/01 1400 <2 <4 <2 <5 <7 <10 <2

21 Sacramento River at Tower Bridge 2/16/01 1230 <2 <4 <2 <5 <7 <10 <2

Appendix 2. Table 2. Pesticide concentrations in environmental samples from the Sacramento River Basin, California, and surrogate recovery analyzed 

by the U.S. Geological Survey National Water Quality Laboratory. 

[<, less than; E, estimated value; ng/L, nanogram per liter; USGS station identification numbers: Sacramento River at Colusa, 11389500; Feather River 

below Star Bend 390020121344201; Sacramento River at Alamar, 384030121373601; Sacramento River at Tower Bridge, 383430121302001] 
64 Occurrence and Transport of Diazinon, Sacramento River and Selected Tributaries, Calif., during Two Winter Storms, 2001

Site 

no. Site name Date Time Carbaryl(ng/L)

Carbofuran

(ng/L)

Chlorpyrifos

(ng/L)

Cyanazine

(ng/L)

DCPA

(ng/L)

Desethyl 

atrazine

(ng/L)

Diazinon 

surrogate

(percent)

8 Sacramento River at Colusa 1/24/01 0940 <41 <20 <5 <.018 <3 <6 98

8 Sacramento River at Colusa 1/25/01 1020 <41 <20 <5 <.018 <3 <6 101

8 Sacramento River at Colusa 1/26/01 0940 <41 <20 <5 <.018 <3 <6 97

8 Sacramento River at Colusa 1/27/01 1040 <41 <20 <5 <.018 <3 <6 122

8 Sacramento River at Colusa 1/28/01 0940 <41 <20 <5 <.018 <3 <6 79

8 Sacramento River at Colusa 2/10/01 0930 <41 <20 <5 <.018 <3 <6 89

8 Sacramento River at Colusa 2/11/01 1040 <41 <20 <5 <.018 <3 <6 94

8 Sacramento River at Colusa 2/12/01 1040 <41 <20 <5 <.018 <3 <6 101

8 Sacramento River at Colusa 2/13/01 0930 <41 <20 <5 <.018 <3 <6 104

8 Sacramento River at Colusa 2/14/01 1000 <41 <20 <5 <.018 <3 <6 99

18 Feather River Below Star Bend 1/24/01 1520 <41 <20 <5 <.018 <3 <6 102

18 Feather River Below Star Bend 1/25/01 1300 E4 <20 <5 <.018 <3 <6 103

18 Feather River Below Star Bend 1/26/01 1400 <40 <20 E2 <.018 <3 <6 111

18 Feather River Below Star Bend 1/27/01 1330 <41 <20 E2 <.018 <3 <6 113

18 Feather River Below Star Bend 1/28/01 1230 <41 <20 <5 <.018 <3 <6 111

18 Feather River Below Star Bend 2/10/01 1300 <41 <20 <5 <.018 <3 <6 86

18 Feather River Below Star Bend 2/11/01 1330 <41 <20 <5 <.018 <3 <6 98

18 Feather River Below Star Bend 2/12/01 1300 <41 <20 <5 <.018 <3 <6 102

18 Feather River Below Star Bend 2/13/01 1130 <41 <20 <5 <.018 <3 <6 105

18 Feather River Below Star Bend 2/14/01 1040 <41 E9 <5 <.018 <3 <6 131

20 Sacramento River at Alamar 1/24/01 1010 E4 E6 <5 <.018 <3 <6 101

20 Sacramento River at Alamar 1/25/01 1110 E4 E6 <5 <.018 <3 <6 104

20 Sacramento River at Alamar 1/26/01 0840 E21 <20 E2 <.018 <3 <6 60

20 Sacramento River at Alamar 1/27/01 1110 E34 <20 E2 <.018 <3 <6 87

20 Sacramento River at Alamar 1/28/01 1050 E4 <20 <5 <.018 <3 <6 101

20 Sacramento River at Alamar 2/9/01 0930 <41 <20 <5 <.018 <3 <6 96

20 Sacramento River at Alamar 2/10/01 1050 <41 <20 <5 <.018 <3 <6 97

20 Sacramento River at Alamar 2/11/01 1030 E3 E7 <5 <.018 <3 <6 108

20 Sacramento River at Alamar 2/12/01 1040 <41 <20 <5 <.018 <3 <6 98

20 Sacramento River at Alamar 2/13/01 1110 E3 <20 <5 <.018 <3 <6 101

20 Sacramento River at Alamar 2/14/01 1010 E3 E5 <5 <.018 <3 <6 107

21 Sacramento River at Tower Bridge 1/25/01 0900 E4 E7 <5 <.018 <3 <6 97

21 Sacramento River at Tower Bridge 1/26/01 1100 E4 <20 <5 <.018 <3 <6 101

21 Sacramento River at Tower Bridge 1/27/01 1100 <41 <20 <5 <.018 <3 <6 97

21 Sacramento River at Tower Bridge 1/28/01 0800 <41 <20 <5 <.018 <3 <6 90

21 Sacramento River at Tower Bridge 1/29/01 1100 <41 <20 <5 <.018 <3 <6 95

21 Sacramento River at Tower Bridge 1/31/01 1130 <41 <20 <5 <.018 <3 <6 128

21 Sacramento River at Tower Bridge 2/10/01 1600 <41 <20 <5 <.018 <3 <6 91

21 Sacramento River at Tower Bridge 2/11/01 1300 <41 <20 <5 <.018 <3 <6 101

21 Sacramento River at Tower Bridge 2/12/01 1300 <41 <20 <5 <.018 <3 <6 97

21 Sacramento River at Tower Bridge 2/13/01 1330 <41 <20 <5 <.018 <3 <6 112

21 Sacramento River at Tower Bridge 2/14/01 1400 <41 <20 <5 <.018 <3 <6 111

21 Sacramento River at Tower Bridge 2/16/01 1230 E4 <20 <5 <.018 <3 <6 121

Appendix 2. Table 2. Pesticide concentrations in environmental samples from the Sacramento River Basin, California, and surrogate recovery analyzed 

by the U.S. Geological Survey National Water Quality Laboratory—Continued. 
Appendix 2. Table 2. 65

Site 

no. Site name Date Time Diazinon(ng/L)

Dieldrin

(ng/L)

Disulfoton

(ng/L)

EPTC

(ng/L)

Ethalfluralin

(ng/L)

Ethoprop

(ng/L)

Fonofos

(ng/L)

8 Sacramento River at Colusa 1/24/01 0940 12 <5 <.021 <2 <9 <5 <3

8 Sacramento River at Colusa 1/25/01 1020 16 <5 <.021 <2 <9 <5 <3

8 Sacramento River at Colusa 1/26/01 0940 36 <5 <.021 <2 <9 <5 <3

8 Sacramento River at Colusa 1/27/01 1040 53 <5 <.021 <2 <9 <5 <3

8 Sacramento River at Colusa 1/28/01 0940 27 <5 <.021 <2 <9 <5 <3

8 Sacramento River at Colusa 2/10/01 0930 <5 <5 <.021 <2 <9 <5 <3

8 Sacramento River at Colusa 2/11/01 1040 7 <5 <.021 <2 <9 <5 <3

8 Sacramento River at Colusa 2/12/01 1040 15 <5 <.021 <2 <9 <5 <3

8 Sacramento River at Colusa 2/13/01 0930 9 <5 <.021 <2 <9 <5 <3

8 Sacramento River at Colusa 2/14/01 1000 10 <5 <.021 <2 <9 <5 <3

18 Feather River Below Star Bend 1/24/01 1520 31 <5 <.021 <2 <9 <5 <3

18 Feather River Below Star Bend 1/25/01 1300 15 <5 <.021 <2 <9 <5 <3

18 Feather River Below Star Bend 1/26/01 1400 26 <5 <.021 <2 <9 <5 <3

18 Feather River Below Star Bend 1/27/01 1330 15 <5 <.021 <2 <9 <5 <3

18 Feather River Below Star Bend 1/28/01 1230 9 <5 <.021 <2 <9 <5 <3

18 Feather River Below Star Bend 2/10/01 1300 15 <5 <.021 <2 <9 <5 <3

18 Feather River Below Star Bend 2/11/01 1330 12 <5 <.021 <2 <9 <5 <3

18 Feather River Below Star Bend 2/12/01 1300 13 <5 <.021 <2 <9 <5 <3

18 Feather River Below Star Bend 2/13/01 1130 14 <5 <.021 <2 <9 <5 <3

18 Feather River Below Star Bend 2/14/01 1040 24 <5 <.021 <2 <9 <5 <3

20 Sacramento River at Alamar 1/24/01 1010 20 <5 <.021 <2 <9 <5 <3

20 Sacramento River at Alamar 1/25/01 1110 24 <5 <.021 <2 <9 E5 <3

20 Sacramento River at Alamar 1/26/01 0840 16 <5 <.021 <2 <9 <5 <3

20 Sacramento River at Alamar 1/27/01 1110 37 <5 <.021 <2 <9 <5 <3

20 Sacramento River at Alamar 1/28/01 1050 84 <5 <.021 <2 <9 <5 <3

20 Sacramento River at Alamar 2/9/01 0930 13 <5 <.021 <2 <9 <5 <3

20 Sacramento River at Alamar 2/10/01 1050 13 <5 <.021 <2 <9 <5 <3

20 Sacramento River at Alamar 2/11/01 1030 17 <5 <.021 <2 <9 <5 <3

20 Sacramento River at Alamar 2/12/01 1040 21 <5 <.021 <2 <9 <5 <3

20 Sacramento River at Alamar 2/13/01 1110 21 <5 <.021 <2 <9 <5 <3

20 Sacramento River at Alamar 2/14/01 1010 27 <5 <.021 <2 <9 <5 <3

21 Sacramento River at Tower Bridge 1/25/01 0900 18 <5 <.021 <2 <9 <5 <3

21 Sacramento River at Tower Bridge 1/26/01 1100 20 <5 <.021 <2 <9 <5 <3

21 Sacramento River at Tower Bridge 1/27/01 1100 45 <5 <.021 <2 <9 <5 <3

21 Sacramento River at Tower Bridge 1/28/01 0800 96 <5 <.021 <2 <9 <5 <3

21 Sacramento River at Tower Bridge 1/29/01 1100 61 <5 <.021 <2 <9 <5 <3

21 Sacramento River at Tower Bridge 1/31/01 1130 30 <5 <.021 <2 <9 <5 <3

21 Sacramento River at Tower Bridge 2/10/01 1600 9 <5 <.021 <2 <9 <5 <3

21 Sacramento River at Tower Bridge 2/11/01 1300 11 <5 <.021 <2 <9 <5 <3

21 Sacramento River at Tower Bridge 2/12/01 1300 14 <5 <.021 <2 <9 <5 <3

21 Sacramento River at Tower Bridge 2/13/01 1330 16 <5 <.021 <2 <9 <5 <3

21 Sacramento River at Tower Bridge 2/14/01 1400 28 <5 <.021 <2 <9 <5 <3

21 Sacramento River at Tower Bridge 2/16/01 1230 18 <5 <.021 <2 <9 <5 <3

Appendix 2. Table 2. Pesticide concentrations in environmental samples from the Sacramento River Basin, California, and surrogate recovery analyzed 

by the U.S. Geological Survey National Water Quality Laboratory—Continued. 
66 Occurrence and Transport of Diazinon, Sacramento River and Selected Tributaries, Calif., during Two Winter Storms, 2001

Site 

no. Site name Date Time

alpha D6 

HCH

(percent)

Lindane

(ng/L)

Linuron

(ng/L)

Malathion

(ng/L)

Methyl 

azinphos

(ng/L)

Methyl 

parathion

(ng/L)

Metolachlor

(ng/L)

8 Sacramento River at Colusa 1/24/01 0940 97 <4 <35 <27 <50 <6 <13

8 Sacramento River at Colusa 1/25/01 1020 103 <4 <35 <27 <50 <6 <13

8 Sacramento River at Colusa 1/26/01 0940 85 <4 <35 <27 <50 <6 E4

8 Sacramento River at Colusa 1/27/01 1040 122 <4 <35 <27 <50 <6 <13

8 Sacramento River at Colusa 1/28/01 0940 69 <4 <35 <27 <50 <6 <13

8 Sacramento River at Colusa 2/10/01 0930 70 <4 <35 <27 <50 <6 <13

8 Sacramento River at Colusa 2/11/01 1040 79 <4 <35 <27 <50 <6 <13

8 Sacramento River at Colusa 2/12/01 1040 77 <4 <35 <27 <50 <6 <13

8 Sacramento River at Colusa 2/13/01 0930 99 <4 <35 <27 <50 <6 <13

8 Sacramento River at Colusa 2/14/01 1000 114 <4 <35 <27 <50 <6 <13

18 Feather River Below Star Bend 1/24/01 1520 106 <4 <35 <27 <50 <6 <13

18 Feather River Below Star Bend 1/25/01 1300 100 <4 <35 <27 <50 <6 <13

18 Feather River Below Star Bend 1/26/01 1400 108 <4 <35 <27 <50 <6 <13

18 Feather River Below Star Bend 1/27/01 1330 108 <4 <35 <27 <50 <6 <13

18 Feather River Below Star Bend 1/28/01 1230 106 <4 <35 <27 <50 <6 <13

18 Feather River Below Star Bend 2/10/01 1300 75 <4 <35 <27 <50 <6 <13

18 Feather River Below Star Bend 2/11/01 1330 84 <4 <35 <27 <50 <6 <13

18 Feather River Below Star Bend 2/12/01 1300 80 <4 <35 <27 <50 <6 <13

18 Feather River Below Star Bend 2/13/01 1130 111 <4 <35 <27 <50 <6 <13

18 Feather River Below Star Bend 2/14/01 1040 182 <4 <35 <27 <50 <6 <13

20 Sacramento River at Alamar 1/24/01 1010 100 <4 <35 <27 <50 <6 E1

20 Sacramento River at Alamar 1/25/01 1110 103 <4 <35 <27 <50 <6 E1

20 Sacramento River at Alamar 1/26/01 0840 60 <4 <35 <27 <50 <6 E5

20 Sacramento River at Alamar 1/27/01 1110 84 <4 <35 <27 <50 <6 E5

20 Sacramento River at Alamar 1/28/01 1050 99 <4 <35 <27 <50 <6 E3

20 Sacramento River at Alamar 2/9/01 0930 76 <4 <35 <27 <50 <6 <13

20 Sacramento River at Alamar 2/10/01 1050 66 <4 <35 <27 <50 <6 <13

20 Sacramento River at Alamar 2/11/01 1030 107 <4 <35 <27 <50 <6 E2

20 Sacramento River at Alamar 2/12/01 1040 106 <4 <35 <27 <50 <6 <13

20 Sacramento River at Alamar 2/13/01 1110 95 <4 <35 <27 <50 <6 E5

20 Sacramento River at Alamar 2/14/01 1010 110 <4 <35 <27 <50 <6 E6

21 Sacramento River at Tower Bridge 1/25/01 0900 99 <4 <35 <27 <50 <6 E1

21 Sacramento River at Tower Bridge 1/26/01 1100 101 <4 <35 <27 <50 <6 E2

21 Sacramento River at Tower Bridge 1/27/01 1100 80 <4 <35 <27 <50 <6 <13

21 Sacramento River at Tower Bridge 1/28/01 0800 76 <4 <35 <27 <50 <6 <13

21 Sacramento River at Tower Bridge 1/29/01 1100 75 <4 <35 <27 <50 <6 <13

21 Sacramento River at Tower Bridge 1/31/01 1130 120 <4 <35 <27 <50 <6 E5

21 Sacramento River at Tower Bridge 2/10/01 1600 67 <4 <35 <27 <50 <6 <13

21 Sacramento River at Tower Bridge 2/11/01 1300 71 <4 <35 <27 <50 <6 <13

21 Sacramento River at Tower Bridge 2/12/01 1300 76 <4 <35 <27 <50 <6 <13

21 Sacramento River at Tower Bridge 2/13/01 1330 109 <4 <35 <27 <50 <6 E3

21 Sacramento River at Tower Bridge 2/14/01 1400 132 <4 <35 <27 <50 <6 E5

21 Sacramento River at Tower Bridge 2/16/01 1230 113 <4 <35 <27 <50 <6 E1

Appendix 2. Table 2. Pesticide concentrations in environmental samples from the Sacramento River Basin, California, and surrogate recovery analyzed

by the U.S. Geological Survey National Water Quality Laboratory—Continued. 
Appendix 2. Table 2. 67

Site 

no. Site name Date Time Metribuzin(ng/L)

Molinate

(ng/L)

Napropamide

(ng/L)

p,p'-DDE

(ng/L)

Parathion

(ng/L)

Pebulate

(ng/L)

Pendimethalin

(ng/L)

8 Sacramento River at Colusa 1/24/01 0940 <6 <2 <7 <3 <7 <2 <10

8 Sacramento River at Colusa 1/25/01 1020 <6 <2 <7 <3 <7 <2 <10

8 Sacramento River at Colusa 1/26/01 0940 <6 <2 <7 <3 <7 <2 <10

8 Sacramento River at Colusa 1/27/01 1040 <6 <2 <7 <3 <7 <2 <10

8 Sacramento River at Colusa 1/28/01 0940 <6 <2 <7 <3 <7 <2 <10

8 Sacramento River at Colusa 2/10/01 0930 <6 <2 <7 <3 <7 <2 <10

8 Sacramento River at Colusa 2/11/01 1040 <6 <2 <7 <3 <7 <2 <10

8 Sacramento River at Colusa 2/12/01 1040 <6 <2 <7 <3 <7 <2 <10

8 Sacramento River at Colusa 2/13/01 0930 <6 <2 <7 <3 <7 <2 <10

8 Sacramento River at Colusa 2/14/01 1000 <6 <2 <7 <3 <7 <2 <10

18 Feather River Below Star Bend 1/24/01 1520 <6 27 <7 <3 <7 <2 <10

18 Feather River Below Star Bend 1/25/01 1300 <6 20 <7 <3 <7 <2 <10

18 Feather River Below Star Bend 1/26/01 1400 <6 25 <7 <3 <7 <2 <10

18 Feather River Below Star Bend 1/27/01 1330 <6 14 <7 <3 <7 <2 <10

18 Feather River Below Star Bend 1/28/01 1230 <6 11 <7 <3 <7 <2 <10

18 Feather River Below Star Bend 2/10/01 1300 <6 16 <7 <3 <7 <2 <10

18 Feather River Below Star Bend 2/11/01 1330 <6 15 <7 <3 <7 <2 <10

18 Feather River Below Star Bend 2/12/01 1300 <6 11 10 <3 <7 <2 <10

18 Feather River Below Star Bend 2/13/01 1130 <6 11 <7 <3 <7 <2 <10

18 Feather River Below Star Bend 2/14/01 1040 <6 7 <7 <3 <7 <2 <10

20 Sacramento River at Alamar 1/24/01 1010 <6 18 <7 <3 <7 <2 <10

20 Sacramento River at Alamar 1/25/01 1110 <6 23 <7 <3 <7 <2 <10

20 Sacramento River at Alamar 1/26/01 0840 <6 26 E3 <3 <7 <2 <10

20 Sacramento River at Alamar 1/27/01 1110 E5 15 E5 <3 <7 <2 <10

20 Sacramento River at Alamar 1/28/01 1050 <6 14 <7 <3 <7 <2 <10

20 Sacramento River at Alamar 2/9/01 0930 <6 19 <7 <3 <7 <2 <10

20 Sacramento River at Alamar 2/10/01 1050 <6 18 <7 <3 <7 <2 <10

20 Sacramento River at Alamar 2/11/01 1030 <6 20 <7 <3 <7 <2 <10

20 Sacramento River at Alamar 2/12/01 1040 <6 21 <7 <3 <7 <2 <10

20 Sacramento River at Alamar 2/13/01 1110 6 19 9 <3 <7 <2 <10

20 Sacramento River at Alamar 2/14/01 1010 10 18 <7 <3 <7 <2 <10

21 Sacramento River at Tower Bridge 1/25/01 0900 <6 21 <7 <3 <7 <2 <10

21 Sacramento River at Tower Bridge 1/26/01 1100 <6 25 <7 <3 <7 <2 <10

21 Sacramento River at Tower Bridge 1/27/01 1100 <6 14 E7 <3 <7 <2 <10

21 Sacramento River at Tower Bridge 1/28/01 0800 <6 <2 <7 <3 <7 <2 <10

21 Sacramento River at Tower Bridge 1/29/01 1100 <6 11 <7 <3 <7 <2 <10

21 Sacramento River at Tower Bridge 1/31/01 1130 <6 21 E6 <3 <7 <2 <10

21 Sacramento River at Tower Bridge 2/10/01 1600 <6 19 <7 <3 <7 <2 <10

21 Sacramento River at Tower Bridge 2/11/01 1300 <6 22 <7 <3 <7 <2 <10

21 Sacramento River at Tower Bridge 2/12/01 1300 <6 19 <7 <3 <7 <2 <10

21 Sacramento River at Tower Bridge 2/13/01 1330 <6 16 <7 <3 <7 <2 <10

21 Sacramento River at Tower Bridge 2/14/01 1400 16 16 <7 <3 <7 <2 <10

21 Sacramento River at Tower Bridge 2/16/01 1230 <6 12 <7 <3 <7 <2 <10

Appendix 2. Table 2. Pesticide concentrations in environmental samples from the Sacramento River Basin, California, and surrogate recovery analyzed

by the U.S. Geological Survey National Water Quality Laboratory—Continued. 
68 Occurrence and Transport of Diazinon, Sacramento River and Selected Tributaries, Calif., during Two Winter Storms, 2001

Site 

no. Site name Date Time Permethrin(ng/L)

Phorate

(ng/L)

Prometon

(ng/L)

Pronamide

(ng/L)

Propachlor

(ng/L)

Propanil

(ng/L)

Propargite

(ng/L)

8 Sacramento River at Colusa 1/24/01 0940 <6 <11 <.015 <4 <10 <11 <23

8 Sacramento River at Colusa 1/25/01 1020 <6 <11 <.015 <4 <10 <11 <23

8 Sacramento River at Colusa 1/26/01 0940 <6 <11 <.015 <4 <10 <11 <23

8 Sacramento River at Colusa 1/27/01 1040 <6 <11 <.015 <4 <10 <11 <23

8 Sacramento River at Colusa 1/28/01 0940 <6 <11 <.015 <4 <10 <11 <23

8 Sacramento River at Colusa 2/10/01 0930 <6 <11 <.015 <4 <10 <11 <23

8 Sacramento River at Colusa 2/11/01 1040 <6 <11 <.015 <4 <10 <11 <23

8 Sacramento River at Colusa 2/12/01 1040 <6 <11 <.015 <4 <10 <11 <23

8 Sacramento River at Colusa 2/13/01 0930 <6 <11 <.015 <4 <10 <11 <23

8 Sacramento River at Colusa 2/14/01 1000 <6 <11 <.015 <4 <10 <11 <23

18 Feather River Below Star Bend 1/24/01 1520 <6 <11 <.015 <4 <10 <11 <23

18 Feather River Below Star Bend 1/25/01 1300 <6 <11 <.015 <4 <10 <11 <23

18 Feather River Below Star Bend 1/26/01 1400 <6 <11 <.015 <4 <10 <11 <23

18 Feather River Below Star Bend 1/27/01 1330 <6 <11 <.015 <4 <10 E3 <23

18 Feather River Below Star Bend 1/28/01 1230 <6 <11 <.015 <4 <10 E2 <23

18 Feather River Below Star Bend 2/10/01 1300 <6 <11 <.015 <4 <10 <11 <23

18 Feather River Below Star Bend 2/11/01 1330 <6 <11 <.015 <4 <10 <11 <23

18 Feather River Below Star Bend 2/12/01 1300 <6 <11 <.015 <4 <10 <11 <23

18 Feather River Below Star Bend 2/13/01 1130 <6 <11 <.015 <4 <10 <11 <23

18 Feather River Below Star Bend 2/14/01 1040 <6 <11 <.015 <4 <10 <11 <23

20 Sacramento River at Alamar 1/24/01 1010 <6 <11 <.015 4 <10 <11 <23

20 Sacramento River at Alamar 1/25/01 1110 <6 <11 <.015 <4 <10 <11 <23

20 Sacramento River at Alamar 1/26/01 0840 <6 <11 <.015 <4 <10 E2 <23

20 Sacramento River at Alamar 1/27/01 1110 <6 <11 <.015 E3 <10 E2 <23

20 Sacramento River at Alamar 1/28/01 1050 <6 <11 <.015 <4 <10 <11 <23

20 Sacramento River at Alamar 2/9/01 0930 <6 <11 <.015 <4 <10 <11 <23

20 Sacramento River at Alamar 2/10/01 1050 <6 <11 <.015 7 <10 <11 <23

20 Sacramento River at Alamar 2/11/01 1030 <6 <11 <.015 10 <10 <11 <23

20 Sacramento River at Alamar 2/12/01 1040 <6 <11 <.015 5 <10 <11 <23

20 Sacramento River at Alamar 2/13/01 1110 <6 <11 <.015 6 <10 <11 <23

20 Sacramento River at Alamar 2/14/01 1010 <6 <11 <.015 9 <10 <11 <23

21 Sacramento River at Tower Bridge 1/25/01 0900 <6 <11 <.015 E4 <10 <11 <23

21 Sacramento River at Tower Bridge 1/26/01 1100 <6 <11 <.015 <4 <10 <11 <23

21 Sacramento River at Tower Bridge 1/27/01 1100 <6 <11 <.015 <4 <10 <11 <23

21 Sacramento River at Tower Bridge 1/28/01 0800 <6 <11 <.015 <4 <10 <11 <23

21 Sacramento River at Tower Bridge 1/29/01 1100 <6 <11 <.015 21 <10 <11 <23

21 Sacramento River at Tower Bridge 1/31/01 1130 <6 <11 <.015 17 <10 <11 <23

21 Sacramento River at Tower Bridge 2/10/01 1600 <6 <11 <.015 <4 <10 <11 <23

21 Sacramento River at Tower Bridge 2/11/01 1300 <6 <11 <.015 7 <10 <11 <23

21 Sacramento River at Tower Bridge 2/12/01 1300 <6 <11 <.015 <4 <10 <11 <23

21 Sacramento River at Tower Bridge 2/13/01 1330 <6 <11 <.015 <4 <10 <11 <23

21 Sacramento River at Tower Bridge 2/14/01 1400 <6 <11 <.015 <4 <10 <11 <23

21 Sacramento River at Tower Bridge 2/16/01 1230 <6 <11 <.015 10 <10 <11 <23

Appendix 2. Table 2. Pesticide concentrations in environmental samples from the Sacramento River Basin, California, and surrogate recovery analyzed 

by the U.S. Geological Survey National Water Quality Laboratory—Continued. 
Appendix 2. Table 2. 69

Site 

no. Site name Date Time Simazine(ng/L)

Tebuthiuron

(ng/L)

Terbacil

(ng/L)

Terbufos

(ng/L)

Thiobencarb

(ng/L)

Triallate

(ng/L)

Trifluralin

(ng/L)

8 Sacramento River at Colusa 1/24/01 0940 <11 36 <34 <17 <5 <2 <9

8 Sacramento River at Colusa 1/25/01 1020 <11 <16 <34 <17 <5 <2 <9

8 Sacramento River at Colusa 1/26/01 0940 21 <16 <34 <17 <5 <2 <9

8 Sacramento River at Colusa 1/27/01 1040 64 <16 <34 <17 <5 <2 <9

8 Sacramento River at Colusa 1/28/01 0940 34 <16 <34 <17 <5 <2 <9

8 Sacramento River at Colusa 2/10/01 0930 <11 <16 <34 <17 <5 <2 <9

8 Sacramento River at Colusa 2/11/01 1040 12 <16 <34 <17 <5 <2 <9

8 Sacramento River at Colusa 2/12/01 1040 22 <16 <34 <17 <5 <2 <9

8 Sacramento River at Colusa 2/13/01 0930 15 <16 <34 <17 <5 <2 <9

8 Sacramento River at Colusa 2/14/01 1000 21 <16 <34 <17 <5 <2 <9

18 Feather River Below Star Bend 1/24/01 1520 E9 E10 <34 <17 8 <2 <9

18 Feather River Below Star Bend 1/25/01 1300 E10 E9 <34 <17 7 <2 <9

18 Feather River Below Star Bend 1/26/01 1400 25 E8 <34 <17 7 <2 <9

18 Feather River Below Star Bend 1/27/01 1330 19 E8 <34 <17 E5 <2 <9

18 Feather River Below Star Bend 1/28/01 1230 17 E9 <34 <17 E4 <2 <9

18 Feather River Below Star Bend 2/10/01 1300 <11 <16 <34 <17 <5 <2 <9

18 Feather River Below Star Bend 2/11/01 1330 E5 <16 <34 <17 6 <2 <9

18 Feather River Below Star Bend 2/12/01 1300 12 <16 <34 <17 <5 <2 <9

18 Feather River Below Star Bend 2/13/01 1130 17 <16 <34 <17 E4 <2 <9

18 Feather River Below Star Bend 2/14/01 1040 23 <16 <34 <17 5 <2 <9

20 Sacramento River at Alamar 1/24/01 1010 E7 E7 <34 <17 7 <2 <9

20 Sacramento River at Alamar 1/25/01 1110 E11 E7 <34 <17 9 <2 <9

20 Sacramento River at Alamar 1/26/01 0840 E7 E6 <34 <17 7 <2 <9

20 Sacramento River at Alamar 1/27/01 1110 19 E7 <34 <17 6 <2 <9

20 Sacramento River at Alamar 1/28/01 1050 73 <16 <34 <17 <5 <2 <9

20 Sacramento River at Alamar 2/9/01 0930 <11 <16 <34 <17 6 <2 <9

20 Sacramento River at Alamar 2/10/01 1050 <11 <16 <34 <17 6 <2 <9

20 Sacramento River at Alamar 2/11/01 1030 E9 <16 <34 <17 8 <2 <9

20 Sacramento River at Alamar 2/12/01 1040 31 <16 <34 <17 6 <2 <9

20 Sacramento River at Alamar 2/13/01 1110 37 <16 <34 <17 7 <2 <9

20 Sacramento River at Alamar 2/14/01 1010 25 <16 <34 <17 7 <2 <9

21 Sacramento River at Tower Bridge 1/25/01 0900 E6 E5 <34 <17 10 <2 <9

21 Sacramento River at Tower Bridge 1/26/01 1100 E6 <16 <34 <17 9 <2 E3

21 Sacramento River at Tower Bridge 1/27/01 1100 20 <16 <34 <17 <5 <2 <9

21 Sacramento River at Tower Bridge 1/28/01 0800 70 <16 <34 <17 <5 <2 <9

21 Sacramento River at Tower Bridge 1/29/01 1100 78 <16 <34 <17 <5 <2 <9

21 Sacramento River at Tower Bridge 1/31/01 1130 26 E9 <34 <17 8 <2 <9

21 Sacramento River at Tower Bridge 2/10/01 1600 <11 <16 <34 <17 5 <2 <9

21 Sacramento River at Tower Bridge 2/11/01 1300 <11 <16 <34 <17 8 <2 <9

21 Sacramento River at Tower Bridge 2/12/01 1300 15 <16 <34 <17 5 <2 <9

21 Sacramento River at Tower Bridge 2/13/01 1330 33 <16 <34 <17 7 <2 <9

21 Sacramento River at Tower Bridge 2/14/01 1400 30 <16 <34 <17 6 <2 <9

21 Sacramento River at Tower Bridge 2/16/01 1230 22 E6 <34 <17 <6 <2 <9

Appendix 2. Table 2. Pesticide concentrations in environmental samples from the Sacramento River Basin, California, and surrogate recovery analyzed 

by the U.S. Geological Survey National Water Quality Laboratory—Continued. 
70 Occurrence and Transport of Diazinon, Sacramento River and Selected Tributaries, Calif., during Two Winter Storms, 2001

Site 

no. Site name Date Time Temperature

(

oC)

Dissolved 

oxygen

(mg/L)

Specific 

conductance

(μS/cm)

pH

Stream 

discharge

(ft3/s)

1 Sacramento River at Hamilton City 02/10/01 1210 — — 160 — 5,925

1 Sacramento River at Hamilton City 02/11/01 1115 — — 134 — 11,700

1 Sacramento River at Hamilton City 02/12/01 1050 — — 138 — 12,700

1 Sacramento River at Hamilton City 02/13/01 1010 — — 121 — 11,600

1 Sacramento River at Hamilton City 02/14/01 1110 — — 124 — 7,840

2 Mud Creek at Chico 02/10/01 1310 — — 710 — —

3 Lindo Creek at Chico 02/10/01 1340 — — 474 — —

4 Big Chico Creek at Chico 02/09/01 1210 5.8 — 132 7.3 —

4 Big Chico Creek at Chico 02/10/01 0850 — — 141 — —

4 Big Chico Creek at Chico 02/10/01 1525 — — 293 — —

4 Big Chico Creek at Chico 02/11/01 0855 — — 129 — —

4 Big Chico Creek at Chico 02/11/01 1510 — — 100 — —

4 Big Chico Creek at Chico 02/12/01 1445 — — 162 — —

4 Big Chico Creek at Chico 02/13/01 0825 — — 121 — —

4 Big Chico Creek at Chico 02/12/01 0835 — — 146 — —

5 Little Chico Creek 02/09/01 1335 7.2 9.8 120 7.1 —

5 Little Chico Creek 02/10/01 1450 — — 196 — —

6 Big Chico Creek at River Road 02/09/01 0920 7.1 4.7 187 7.4 47

6 Big Chico Creek at River Road 02/09/01 1755 — — — — E47

6 Big Chico Creek at River Road 02/10/01 1020 — — 92 — 393

6 Big Chico Creek at River Road 02/10/01 1600 — — 216 — 1,030

6 Big Chico Creek at River Road 02/11/01 0945 — — 75 — 1,490

6 Big Chico Creek at River Road 02/11/01 1725 — — — — 1,430

6 Big Chico Creek at River Road 02/12/01 0920 — — 98 — 883

6 Big Chico Creek at River Road 02/12/01 1515 — — 80 — 870

6 Big Chico Creek at River Road 02/13/01 0900 — — 91 — 397

7 Stony Creek at HW 45 02/09/01 1055 7.6 — 335 8.3 —

7 Stony Creek at HW 45 02/10/01 1120 — — 344 — —

8 Sacramento River at Colusa 01/24/01 1020 9.1 10.9 171 7.9 5,930

8 Sacramento River at Colusa 01/25/01 0944 9.2 6.9 168 8.1 12,600

8 Sacramento River at Colusa 01/26/01 0940 7.6 8.3 116 7.6 15,770

8 Sacramento River at Colusa 01/27/01 1040 6.6 8.5 100 7.7 22,900

8 Sacramento River at Colusa 01/28/01 1020 6.4 8.5 108 7.7 16,100

8 Sacramento River at Colusa 02/10/01 1020 8.0 9.9 184 7.6 5,900

8 Sacramento River at Colusa 02/11/01 1045 7.5 10.2 166 7.9 9,830

8 Sacramento River at Colusa 02/12/01 1045 7.2 10.3 148 7.7 14,100

8 Sacramento River at Colusa 02/13/01 1030 6.7 10.5 — — 14,200

8 Sacramento River at Colusa 02/14/01 1000 7.3 10.0 132 7.6 12,200

9 Butte Creek at Gridley Road 01/24/01 1155 9.1 9.0 244 7.7 —

9 Butte Creek at Gridley Road 01/24/01 2100 9.4 9.7 223 7.8 —

9 Butte Creek at Gridley Road 01/25/01 1025 9.0 9.2 221 7.7 —

9 Butte Creek at Gridley Road 01/25/01 1445 8.5 9.5 223 7.7 —

9 Butte Creek at Gridley Road 01/25/01 1800 8.2 9.5 225 7.7 —

Appendix 2. Table 3.Field measurements at sites in the Sacramento River Basin, California. 

[—, no data reported, E, estimated value; oC, degrees centigrade; mg/L, milligrams per liter; μS/cm, microsiemans per centimeter; ft3/s, cubic feet per second]
Appendix 2. Table 3. 71

9 Butte Creek at Gridley Road 01/25/01 2200 7.7 9.9 223 7.7 —

9 Butte Creek at Gridley Road 01/26/01 0200 7.4 10.0 216 7.7 —

9 Butte Creek at Gridley Road 01/26/01 0620 6.7 9.1 179 7.7 —

9 Butte Creek at Gridley Road 01/26/01 1010 6.6 10.6 154 7.7 —

9 Butte Creek at Gridley Road 01/26/01 1410 7.2 10.5 167 7.8 —

9 Butte Creek at Gridley Road 01/26/01 1800 7.3 10.3 182 7.6 —

9 Butte Creek at Gridley Road 01/26/01 2200 7.7 10.4 181 7.6 —

9 Butte Creek at Gridley Road 01/27/01 0000 7.4 10.5 202 8.1 —

9 Butte Creek at Gridley Road 01/27/01 0200 8.0 10.0 190 7.7 —

9 Butte Creek at Gridley Road 01/27/01 0625 7.6 9.9 192 7.6 —

9 Butte Creek at Gridley Road 01/27/01 1205 7.0 9.7 197 7.8 —

9 Butte Creek at Gridley Road 01/27/01 1800 7.3 10.4 201 7.8 —

9 Butte Creek at Gridley Road 01/28/01 0745 7.4 9.5 208 7.8 —

9 Butte Creek at Gridley Road 02/09/01 1815 8.0 8.5 296 8.0 —

9 Butte Creek at Gridley Road 02/09/01 2217 7.8 9.2 296 7.8 —

9 Butte Creek at Gridley Road 02/10/01 0220 7.5 9.8 290 7.9 —

9 Butte Creek at Gridley Road 02/10/01 0615 7.2 — — 7.7 —

9 Butte Creek at Gridley Road 02/10/01 1030 7.1 — — 7.7 —

9 Butte Creek at Gridley Road 02/10/01 1855 7.3 10.5 232 7.8 —

9 Butte Creek at Gridley Road 02/10/01 2205 7.4 10.2 — 7.9 —

9 Butte Creek at Gridley Road 02/11/01 0210 7.3 9.9 189 7.8 —

9 Butte Creek at Gridley Road 02/11/01 0610 7.6 12.4 — 7.8 —

9 Butte Creek at Gridley Road 02/11/01 2205 7.2 10.6 142 7.7 —

9 Butte Creek at Gridley Road 02/12/01 0005 7.2 10.6 173 7.7 —

9 Butte Creek at Gridley Road 02/12/01 0210 7.5 10.4 152 7.6 —

9 Butte Creek at Gridley Road 02/12/01 0620 7.4 10.0 162 7.7 —

9 Butte Creek at Gridley Road 02/12/01 1815 7.2 11.7 — 7.8 —

9 Butte Creek at Gridley Road 02/13/01 1030 6.9 10.6 208 7.7 —

9 Butte Creek at Gridley Road 02/11/01 1800 7.2 10.7 182 7.9 —

10 Main Drainage Canal at Gridley Road 01/24/01 1220 10.6 8.8 274 7.7 118

10 Main Drainage Canal at Gridley Road 01/24/01 2135 11.4 8.0 274 — 120

10 Main Drainage Canal at Gridley Road 01/25/01 1045 8.3 8.5 285 7.7 107

10 Main Drainage Canal at Gridley Road 01/25/01 1510 8.2 9.7 280 7.8 128

10 Main Drainage Canal at Gridley Road 01/25/01 1830 8.0 5.8 253 7.8 159

10 Main Drainage Canal at Gridley Road 01/25/01 2230 7.7 9.1 240 7.6 217

10 Main Drainage Canal at Gridley Road 01/26/01 0230 7.2 8.8 218 7.8 215

10 Main Drainage Canal at Gridley Road 01/26/01 0635 7.2 7.7 228 7.6 203

10 Main Drainage Canal at Gridley Road 01/26/01 1025 7.6 9.0 239 7.5 194

10 Main Drainage Canal at Gridley Road 01/26/01 1440 9.8 9.5 240 7.7 182

10 Main Drainage Canal at Gridley Road 01/26/01 1830 10.1 9.5 244 7.6 169

10 Main Drainage Canal at Gridley Road 01/26/01 2230 9.2 8.7 253 7.6 158

10 Main Drainage Canal at Gridley Road 01/27/01 0030 9.1 8.8 280 7.7 153

10 Main Drainage Canal at Gridley Road 01/27/01 0230 8.2 8.6 260 7.6 143

10 Main Drainage Canal at Gridley Road 01/27/01 0650 6.7 8.9 266 7.6 133

Site 

no. Site name Date Time Temperature

(

oC)

Dissolved 

oxygen

(mg/L)

Specific 

conductance

(μS/cm)

pH

Stream 

discharge

(ft3

/s)

Appendix 2. Table 3.Field measurements at sites in the Sacramento River Basin, California—Continued. 
72 Occurrence and Transport of Diazinon, Sacramento River and Selected Tributaries, Calif., during Two Winter Storms, 2001

10 Main Drainage Canal at Gridley Road 01/27/01 1240 7.8 10.2 270 7.9 131

10 Main Drainage Canal at Gridley Road 01/27/01 1830 10.2 10.4 278 8.0 136

10 Main Drainage Canal at Gridley Road 01/28/01 0810 7.1 8.5 295 7.6 139

10 Main Drainage Canal at Gridley Road 02/09/01 1836 8.9 10.2 349 8.1 80

10 Main Drainage Canal at Gridley Road 02/09/01 2240 8.5 8.5 307 7.8 99

10 Main Drainage Canal at Gridley Road 02/10/01 0238 7.5 8.0 281 7.9 95

10 Main Drainage Canal at Gridley Road 02/10/01 0635 6.6 — — 7.6 93

10 Main Drainage Canal at Gridley Road 02/10/01 1055 8.0 — — 7.7 90

10 Main Drainage Canal at Gridley Road 02/10/01 1540 — — — — 88

10 Main Drainage Canal at Gridley Road 02/10/01 1910 10.5 9.4 330 7.7 88

10 Main Drainage Canal at Gridley Road 02/10/01 2220 6.8 11.8 0 7.8 103

10 Main Drainage Canal at Gridley Road 02/11/01 0220 8.8 5.9 297 7.6 117

10 Main Drainage Canal at Gridley Road 02/11/01 0700 7.7 8.5 278 7.7 131

10 Main Drainage Canal at Gridley Road 02/11/01 1030 — — — — 158

10 Main Drainage Canal at Gridley Road 02/11/01 1430 — — — — 173

10 Main Drainage Canal at Gridley Road 02/11/01 1815 9.6 8.8 242 7.8 176

10 Main Drainage Canal at Gridley Road 02/11/01 2220 9.0 8.5 247 7.5 168

10 Main Drainage Canal at Gridley Road 02/12/01 0015 8.7 9.0 287 7.6 161

10 Main Drainage Canal at Gridley Road 02/12/01 0220 8.6 8.3 266 7.5 153

10 Main Drainage Canal at Gridley Road 02/12/01 0640 8.1 7.8 276 7.6 165

10 Main Drainage Canal at Gridley Road 02/12/01 1200 — — — — 198

10 Main Drainage Canal at Gridley Road 02/12/01 1449 — — — — 196

10 Main Drainage Canal at Gridley Road 02/12/01 1830 9.3 9.6 257 7.7 184

10 Main Drainage Canal at Gridley Road 02/13/01 1045 6.8 9.8 336 7.7 127

11 Butte Slough at Lower Pass Road 01/24/01 1144 8.9 9.1 281 7.5 457

11 Butte Slough at Lower Pass Road 01/25/01 1125 8.7 6.5 281 7.7 664

11 Butte Slough at Lower Pass Road 01/26/01 1120 7.9 6.7 265 7.6 1,220

11 Butte Slough at Lower Pass Road 01/27/01 1120 7.3 6.9 200 7.7 1,430

11 Butte Slough at Lower Pass Road 01/28/01 1115 7.5 6.9 243 7.7 1,360

11 Butte Slough at Lower Pass Road 02/09/01 1200 7.6 9.0 306 7.6 431

11 Butte Slough at Lower Pass Road 02/10/01 1120 7.3 8.6 312 7.7 394

11 Butte Slough at Lower Pass Road 02/11/01 1135 7.9 8.8 274 7.6 542

11 Butte Slough at Lower Pass Road 02/12/01 1115 7.7 8.8 223 7.4 995

11 Butte Slough at Lower Pass Road 02/13/01 1115 7.1 8.6 202 7.6 1,100

11 Butte Slough at Lower Pass Road 02/14/01 1115 7.6 8.5 219 6.9 1,030

12 Wadsworth canal at South Butte Road 01/24/01 2240 10.7 9.0 418 8.0 —

12 Wadsworth canal at South Butte Road 01/25/01 1140 9.9 8.7 412 7.9 —

12 Wadsworth canal at South Butte Road 01/25/01 1900 9.6 9.5 390 7.9 —

12 Wadsworth canal at South Butte Road 01/25/01 2300 6.7 9.7 230 7.2 —

12 Wadsworth canal at South Butte Road 01/26/01 0300 7.6 9.1 333 7.9 —

12 Wadsworth canal at South Butte Road 01/26/01 0730 8.0 — 314 7.8 —

12 Wadsworth canal at South Butte Road 01/26/01 1245 9.0 9.5 327 7.8 —

12 Wadsworth canal at South Butte Road 01/26/01 1650 9.8 9.5 240 7.7 —

12 Wadsworth canal at South Butte Road 01/26/01 1900 9.6 9.5 334 7.8 —

12 Wadsworth canal at South Butte Road 01/26/01 2300 6.9 9.6 340 6.8 —

Site 

no. Site name Date Time Temperature

(

oC)

Dissolved 

oxygen

(mg/L)

Specific 

conductance

(μS/cm)

pH

Stream 

discharge

(ft3/s)

Appendix 2. Table 3.Field measurements at sites in the Sacramento River Basin, California—Continued. 
Appendix 2. Table 3. 73

12 Wadsworth canal at South Butte Road 01/27/01 0300 9.2 8.6 353 7.8 —

12 Wadsworth canal at South Butte Road 01/27/01 0740 8.4 9.2 363 7.9 —

12 Wadsworth canal at South Butte Road 01/27/01 1505 10.2 9.9 376 8.0 —

12 Wadsworth canal at South Butte Road 01/27/01 1900 9.8 10.0 381 7.9 —

12 Wadsworth canal at South Butte Road 01/28/01 0100 9.2 10.0 382 8.0 —

12 Wadsworth canal at South Butte Road 01/28/01 1025 8.7 9.0 386 7.9 —

12 Wadsworth canal at South Butte Road 02/09/01 1920 9.3 8.8 535 8.2 —

12 Wadsworth canal at South Butte Road 02/09/01 2320 9.1 — — 7.9 —

12 Wadsworth canal at South Butte Road 02/10/01 0320 8.4 9.0 491 7.9 —

12 Wadsworth canal at South Butte Road 02/10/01 0735 8.3 — — 7.8 —

12 Wadsworth canal at South Butte Road 02/10/01 2000 9.2 8.9 437 7.9 —

12 Wadsworth canal at South Butte Road 02/10/01 2300 9.3 — — 7.8 —

12 Wadsworth canal at South Butte Road 02/11/01 0300 9.0 8.9 205 7.8 —

12 Wadsworth canal at South Butte Road 02/11/01 0825 8.0 9.1 350 7.8 —

12 Wadsworth canal at South Butte Road 02/11/01 1900 9.0 9.6 267 7.7 —

12 Wadsworth canal at South Butte Road 02/11/01 2300 9.2 9.2 235 7.7 —

12 Wadsworth canal at South Butte Road 02/12/01 0055 8.5 9.6 301 7.7 —

12 Wadsworth canal at South Butte Road 02/12/01 0305 9.3 8.9 203 7.6 —

12 Wadsworth canal at South Butte Road 02/12/01 0725 8.1 9.5 240 7.6 —

12 Wadsworth canal at South Butte Road 02/12/01 1915 8.5 10.1 271 7.7 —

13 DWR Pumping Plant 2, North 01/24/01 1230 10.1 6.0 316 7.3 —

13 DWR Pumping Plant 2, North 01/25/01 1240 9.5 7.6 321 — —

13 DWR Pumping Plant 2, North 01/26/01 1300 8.6 8.1 318 7.4 —

13 DWR Pumping Plant 2, North 01/27/01 1300 8.7 8.8 342 7.7 —

13 DWR Pumping Plant 2, North 01/28/01 1230 8.9 7.2 326 7.5 —

13 DWR Pumping Plant 2, North 02/09/01 1310 8.3 7.7 293 8.0 —

13 DWR Pumping Plant 2, North 02/10/01 1239 8.7 7.9 386 8.1 —

13 DWR Pumping Plant 2, North 02/11/01 1217 9.7 8.2 345 7.9 —

13 DWR Pumping Plant 2, North 02/12/01 1240 9.1 7.8 305 7.6 —

13 DWR Pumping Plant 2, North 02/13/01 1245 8.0 8.2 299 7.7 —

14 DWR Pumping Plant 2, South 01/24/01 1245 10.4 6.3 252 7.3 —

14 DWR Pumping Plant 2, South 01/25/01 1255 9.3 7.9 340 — —

14 DWR Pumping Plant 2, South 01/26/01 1315 8.9 7.9 335 7.3 —

14 DWR Pumping Plant 2, South 01/27/01 1245 9.2 7.7 410 7.6 —

14 DWR Pumping Plant 2, South 01/28/01 1240 8.1 6.1 280 7.6 —

14 DWR Pumping Plant 2, South 02/09/01 1250 9.0 8.0 287 8.0 —

14 DWR Pumping Plant 2, South 02/10/01 1222 8.5 10.4 691 8.5 —

14 DWR Pumping Plant 2, South 02/11/01 1203 9.2 8.8 538 8.3 —

14 DWR Pumping Plant 2, South 02/12/01 1250 9.5 6.6 316 7.7 —

14 DWR Pumping Plant 2, South 02/13/01 1254 9.1 5.6 362 7.8 —

15 DWR Pumping Plant 1 01/24/01 1140 9.0 7.4 — 7.6 —

15 DWR Pumping Plant 1 01/25/01 1210 7.9 9.4 568 — —

15 DWR Pumping Plant 1 01/26/01 1413 8.4 9.5 540 7.6 —

15 DWR Pumping Plant 1 01/27/01 1210 7.8 8.5 648 7.6 —

Site 

no. Site name Date Time Temperature

(

oC)

Dissolved 

oxygen

(mg/L)

Specific 

conductance

(μS/cm)

pH

Stream 

discharge

(ft3

/s)

Appendix 2. Table 3.Field measurements at sites in the Sacramento River Basin, California—Continued. 
74 Occurrence and Transport of Diazinon, Sacramento River and Selected Tributaries, Calif., during Two Winter Storms, 2001

15 DWR Pumping Plant 1 01/28/01 1140 7.6 8.5 530 7.6 —

15 DWR Pumping Plant 1 02/09/01 1210 7.4 7.8 335 8.1 —

15 DWR Pumping Plant 1 02/10/01 1055 7.3 6.4 503 7.9 —

15 DWR Pumping Plant 1 02/11/01 1130 8.5 6.8 482 8.0 —

15 DWR Pumping Plant 1 02/12/01 1200 8.2 7.4 457 7.7 —

15 DWR Pumping Plant 1 02/13/01 1209 7.7 10.5 602 7.9 —

16 Jack Slough near Doc Adams Road 01/24/01 1400 9.3 10.2 120 7.3 133

16 Jack Slough near Doc Adams Road 01/25/01 1400 7.7 7.4 125.8 7.4 135

16 Jack Slough near Doc Adams Road 01/26/01 1320 7.3 7.6 115 7.4 181

16 Jack Slough near Doc Adams Road 01/27/01 1315 7.1 7.7 — 7.5 118

16 Jack Slough near Doc Adams Road 01/28/01 1255 7.2 7.4 131 7.5 109

16 Jack Slough near Doc Adams Road 02/09/01 1315 7.3 7.7 154 7.9 65

16 Jack Slough near Doc Adams Road 02/10/01 1245 6.8 9.4 131 7.0 142

16 Jack Slough near Doc Adams Road 02/11/01 1245 7.5 9.2 127 7.1 206

16 Jack Slough near Doc Adams Road 02/12/01 1300 7.2 9.2 111 6.8 254

16 Jack Slough near Doc Adams Road 02/13/01 1230 6.4 9.4 118 6.8 164

16 Jack Slough near Doc Adams Road 02/14/01 1220 8.2 8.8 130 6.7 125

17 Feather River near Yuba City 01/24/01 1342 9.1 7.8 110 7.5 —

17 Feather River near Yuba City 01/25/01 1325 8.4 7.1 119 7.3 —

17 Feather River near Yuba City 01/26/01 1240 8.6 5.5 115 7.9 —

17 Feather River near Yuba City 01/27/01 1240 8.1 5.6 100 7.8 —

17 Feather River near Yuba City 01/28/01 1230 8.1 6.1 115 8.0 —

17 Feather River near Yuba City 02/10/01 1210 8.1 7.8 110 7.0 —

17 Feather River near Yuba City 02/11/01 1210 7.7 9.1 124 7.0 —

17 Feather River near Yuba City 02/12/01 1230 7.6 7.0 99 7.0 —

17 Feather River near Yuba City 02/13/01 1200 7.7 8.4 105 6.9 —

17 Feather River near Yuba City 02/14/01 1150 8.2 8.9 109 6.8 —

18 Feather River at Star Bend 01/24/01 1520 — — — — 3,130

18 Feather River at Star Bend 01/25/01 1300 — — — — 3,120

18 Feather River at Star Bend 01/26/01 1400 — — — — 3,870

18 Feather River at Star Bend 01/27/01 1330 — — — — 3,630

18 Feather River at Star Bend 01/28/01 1230 — — — — 3,170

18 Feather River at Star Bend 02/10/01 1300 — — — — 3,140

18 Feather River at Star Bend 02/11/01 1300 — — — — 4,250

18 Feather River at Star Bend 02/12/01 1300 — — — — 5,520

18 Feather River at Star Bend 02/13/01 1130 — — — — 4,470

18 Feather River at Star Bend 02/14/01 1040 — — — — 3,570

19 Bear River near Berry Road 01/24/01 1720 8.7 — — — 77

19 Bear River near Berry Road 01/25/01 0930 7.5 — — — 120

19 Bear River near Berry Road 01/26/01 1120 — — — — 223

19 Bear River near Berry Road 01/27/01 1030 — — — — 270

19 Bear River near Berry Road 01/28/01 1000 — — — — 210

19 Bear River near Berry Road 02/09/01 1050 7.0 — — — 79

19 Bear River near Berry Road 02/10/01 1030 6.9 — — — 119

Site 

no. Site name Date Time Temperature

(

oC)

Dissolved 

oxygen

(mg/L)

Specific 

conductance

(μS/cm)

pH

Stream 

discharge

(ft3

/s)

Appendix 2. Table 3.Field measurements at sites in the Sacramento River Basin, California—Continued. 
Appendix 2. Table 3. 75

19 Bear River near Berry Road 02/11/01 1030 — — — — 340

19 Bear River near Berry Road 02/12/01 1100 — — — — 855

19 Bear River near Berry Road 02/13/01 1000 — — — — 550

20 Sacramento River at Alamar 01/24/01 0900 — — — — 12,600

20 Sacramento River at Alamar 01/25/01 1115 8.8 10.7 222 — 13,100

20 Sacramento River at Alamar 01/26/01 0900 — — — — 17,800

20 Sacramento River at Alamar 01/27/01 1115 7.9 11.5 192 7.5 24,700

20 Sacramento River at Alamar 01/28/01 1053 7.1 10.8 158 7.0 26,700

20 Sacramento River at Alamar 02/09/01 0900 — — — — 11,000

20 Sacramento River at Alamar 02/10/01 1050 8.0 10.6 223 8.2 11,500,

20 Sacramento River at Alamar 02/11/01 1100 8.3 10.6 197 8.0 12,500

20 Sacramento River at Alamar 02/12/01 1115 8.1 10.9 204 7.8 17,800

20 Sacramento River at Alamar 02/13/01 1115 7.3 11.1 200 7.7 22,000

20 Sacramento River at Alamar 02/14/01 1010 — — — — 21,600

21 Sacramento River at Tower Bridge 01/25/01 0900 — — — — 14,800

21 Sacramento River at Tower Bridge 01/26/01 1100 — — — — 16,600

21 Sacramento River at Tower Bridge 01/27/01 1100 — — — — 22,800

21 Sacramento River at Tower Bridge 01/28/01 0800 — — — — 29,600

21 Sacramento River at Tower Bridge 01/29/01 1100 — — — — 26,500

21 Sacramento River at Tower Bridge 01/31/01 1130 — — — — 18,700

21 Sacramento River at Tower Bridge 02/10/01 1600 — — — — 15,700

21 Sacramento River at Tower Bridge 02/11/01 1300 — — — — 9,640

21 Sacramento River at Tower Bridge 02/12/01 1300 — — — — 14,700

21 Sacramento River at Tower Bridge 02/13/01 1330 — — — — 20,900

21 Sacramento River at Tower Bridge 02/14/01 1400 — — — — 20,700

21 Sacramento River at Tower Bridge 02/16/01 1230 — — — — 19,200

Site 

no. Site name Date Time Temperature

(

oC)

Dissolved 

oxygen

(mg/L)

Specific 

conductance

(μS/cm)

pH

Stream 

discharge

(ft3

/s)

Appendix 2. Table 3.Field measurements at sites in the Sacramento River Basin, California—Continued.